Add bEventNewPluginOptions event.

When pushing explicit plugin arguments use a new event
bEventNewPluginOptions instead of reusing the bEventPluginCommand
event which is also used when parsing the fileset when doing a backup.

Most plugins should now also allow multiple plugin lines within one
include block of the fileset which was broken when it used the new
config parser. In combination with forcing certain explicit restore
options by the director using the plugin options passing this may lead
to some surprises however so when using specific plugin options its wise
to only restore one file at a time to be sure the right restore options
are used.
BVFS reported a problem for <id> fix.

There was a mixup of the return value returned from the
bvfs_update_path_hierarchy_cache() function which returns a zero which
is interpretted as a false by the calling dot_bvfs_update() function.
Lets return a proper boolean value and only set that return value to
true when we leave the bvfs_update_path_hierarchy_cache() function due
to hitting either an empty jobid list or after processing the jobid list
successfully. Any other exit (due to joblist corruption or failing to
update the path hierarchy cache) leads to the function returning false.

Fixes #217: BVFS reported a problem for <id>
Fix typo.
Copy job definition requires unnecessary settings

Due to implementing this feature we can no longer asume that there
always is a Client and Fileset in a Job definition. So we need to learn
the .defaults cmd that is needs to print *None* when we don't have a
Client or Fileset and not just dereference a NULL pointer.

Fixes #220: Copy job definition requires unnecessary settings
Merge branch 'master' of https://github.com/bareos/bareos