debug: backtrace error path

Add backtrace for 'n' answer.
cleanup: device extent_size first
man: lvmcache

separate man page for lvm cache
tests: drop nosync

Mirrors currently do not support any conversion,
when they are created no-sync.
config: add CONFIG_FILE_SPECIAL config source id

Add CONFIG_FILE_SPECIAL config source id to make a difference between
real configuration tree (like lvm.conf and tag configs) and special purpose
configuration tree (like LVM metadata, persistent filter).

This makes it easier to attach correct customized data to the config
tree that is created out of the source then.
config: attach cft_check_handle to each config tree instead of global cmd_context

Before, the cft_check_handle used to direct configuration checking
was part of cmd_context. It's better to attach this as part of the
exact config tree against which the check is done. This patch moves
the cft_check_handle out of cmd_context and it attaches it to the
config tree directly as dm_config_tree->custom->config_source->check_handle.

This change makes it easier to track the config tree check results
and provides less space for bugs as the results are directly attached
to the tree and we don't need to be cautious whether the global value
is correct or not (and whether it needs reinitialization) as it was
in the case when the cft_check_handle was part of cmd_context.
config: fix incorrect profile initialization on cmd context refresh

When cmd refresh is called, we need to move any already loaded profiles
to profiles_to_load list which will cause their reload on subsequent
use. In addition to that, we need to take into account any change
in config/profile configuration setting on cmd context refresh
since this setting could be overriden with --config.

Also, when running commands in the shell, we need to remove the
global profile used from the configuration cascade so the profile
is not incorrectly reused next time when the --profile option is
not specified anymore for the next command in the shell.

This bug only affected profile specified by --profile cmd line
arg, not profiles referenced from LVM metadata.
dumpconfig: fix dumpconfig --type diff used in lvm shell as second and later command

The dumpconfig reuses existing config_def_check results in case
the check is done during general lvm command context initialization
(when enabled by config/checks=1) so dumpconfig does not need to run
the same check again during its execution, hence saving some time.

However, we don't check for differences from defaults during general
lvm command initialization as it's useless at that time. It makes
sense only in case when such a check is directly requested (like in
the case of lvm dumpconfig --type diff). We need to take care that
the reused information was already produced with this "diff" checking
before and if not, we need to force the check so the check status also
gathers the new "diff" info now.

Also, do not do diff checking for any other dumpconfig command that
is run after dumpconfig --type diff.
commands: do not register profile_ARG for lvcreate/lvchange separetely

The --profile is globally available for all commands.
config: add CFG_PROFILABLE_METADATA flag

Mark profilable settings with a separate CFG_PROFILABLE_METADATA
flag where the profile can be attached to VG/LV. This makes it possible
to differentiate global command-profilable settings (CFG_PROFILABLE flag)
and contextual metadata-profilable (per VG/LV) settings (CFG_PROFILABLE_METADATA flag).
config: differentiate command and metadata profiles and consolidate profile handling code

- When defining configuration source, the code now uses separate
  CONFIG_PROFILE_COMMAND and CONFIG_PROFILE_METADATA markers
  (before, it was just CONFIG_PROFILE that did not make the
  difference between the two). This helps when checking the
  configuration if it contains correct set of options which
  are all in either command-profilable or metadata-profilable
  group without mixing these groups together - so it's a firm
  distinction. The "command profile" can't contain
  "metadata profile" and vice versa! This is strictly checked
  and if the settings are mixed, such profile is rejected and
  it's not used. So in the end, the CONFIG_PROFILE_COMMAND
  set of options and CONFIG_PROFILE_METADATA are mutually exclusive
  sets.

- Marking configuration with one or the other marker will also
  determine the way these configuration sources are positioned
  in the configuration cascade which is now:

  CONFIG_STRING -> CONFIG_PROFILE_COMMAND -> CONFIG_PROFILE_METADATA -> CONFIG_FILE/CONFIG_MERGED_FILES

- Marking configuration with one or the other marker will also make
  it possible to issue a command context refresh (will be probably
  a part of a future patch) if needed for settings in global profile
  set. For settings in metadata profile set this is impossible since
  we can't refresh cmd context in the middle of reading VG/LV metadata
  and for each VG/LV separately because each VG/LV can have a different
  metadata profile assinged and it's not possible to change these
  settings at this level.

- When command profile is incorrect, it's rejected *and also* the
  command exits immediately - the profile *must* be correct for the
  command that was run with a profile to be executed. Before this
  patch, when the profile was found incorrect, there was just the
  warning message and the command continued without profile applied.
  But it's more correct to exit immediately in this case.

- When metadata profile is incorrect, we reject it during command
  runtime (as we know the profile name from metadata and not early
  from command line as it is in case of command profiles) and we
  *do continue* with the command as we're in the middle of operation.
  Also, the metadata profile is applied directly and on the fly on
  find_config_tree_* fn call and even if the metadata profile is
  found incorrect, we still need to return the non-profiled value
  as found in the other configuration provided or default value.
  To exit immediately even in this case, we'd need to refactor
  existing find_config_tree_* fns so they can return error. Currently,
  these fns return only config values (which end up with default
  values in the end if the config is not found).

- To check the profile validity before use to be sure it's correct,
  one can use :

    lvm dumpconfig --commandprofile/--metadataprofile ProfileName --validate

  (the --commandprofile/--metadataprofile for dumpconfig will come
   as part of the subsequent patch)

- This patch also adds a reference to --commandprofile and
  --metadataprofile in the cmd help string (which was missing before
  for the --profile for some commands). We do not mention --profile
  now as people should use --commandprofile or --metadataprofile
  directly. However, the --profile is still supported for backward
  compatibility and it's translated as:

    --profile == --metadataprofile for lvcreate, vgcreate, lvchange and vgchange
                 (as these commands are able to attach profile to metadata)

    --profile == --commandprofile for all the other commands
                (--metadataprofile is not allowed there as it makes no sense)

- This patch also contains some cleanups to make the code handling
  the profiles more readable...
dumpconfig: add --type profilable-command/profilable-metadata, --metadataprofile/--commandprofile

The dumpconfig now understands --commandprofile/--profile/--metadataprofile

The --commandprofile and --profile functionality is almost the same
with only one difference and that is that the --profile is just used
for dumping the content, it's not applied for the command itself
(while the --commandprofile profile is applied like it is done for
any other LVM command).

We also allow --metadataprofile for dumpconfig - dumpconfig *does not*
touch VG/LV and metadata in any way so it's OK to use it here (just for
dumping the content, checking the profile validity etc.).

The validity of the profile can be checked with:
      dumpconfig --commandprofile/--profile/--metadataprofile --validate

...depending on the profile type.

Also, mention --config in the dumpconfig help string so users know
that  dumpconfig handles this too (it did even before, but it was not
documented in the help string).
tests: update profiles.sh test for latest changes
thin: lvconvert warn before conversion

Warn user before converting volume to different type.

  WARNING: Converting vg/lvol0 logical volume to pool's meta/data volume.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)

Since the content of volume is lost we have to query user to confirm
such operation.  If user is 100% sure, he may use '--yes' to avoid prompts.
lvconvert: check ret code of mirror_remove_missing

When mirror_remove_missing() fails, stop repairing mirror.
debug: fix backtracing
man: cleanup style
cleanup: unneeded initialization

Move or drop initialization where it is not needed.
cleanup: indent
cleanup: use print when displaying info

Use error or warn only when we really have some problem in the code.