cpu plugin: Various, random fixes and improvements:

* Add Pierre-Yves to the list of copyright holders.
* Make sure the entire file is consistently indented.
* Renamed the "ReportActive" config option to "ReportByState"
  (with negated logic).
* Renamed internal functions to better reflect their use.
* Let cpu_stage() (née submit()) work on individual counters / derives
  rather than an array, removing logic from the cpu_read() function.
* Rename CPU_SUBMIT_* to CPU_STATE_*.
* Move legacy behavior it its own function, cpu_commit_without_aggregation().
src/collectd.c: Set the LC_NUMERIC locale to "C".

When using ASCII protocols, such as the Graphite protocol, doubles are
converted to strings using sprintf(3) and parsed with strtod(3). If the
effective locale uses something different from a dot (".") as the
decimal separator (e.g. Portuguese, German), this breaks.

This patch sets the LC_NUMERIC locale to "C" on start-up, so that
strings are produced and parsed in a well-defined manner.

Fixes: #512
memory: adjust safeguard to changes from previous commit
memory: make linux slab reporting work with older kernels
Move collectd daemon files to the src/daemon/ directory.
common.[ch]: Move escape_string() to here.
Move utils_parse_option.[ch] out of the daemon/ directory.
COPYING: Add the MIT License and add a note about plugins being licensed individually.
bind plugin: add support for the new XML v3 API.

Unfortunately, this new API does not provide per-zone data
any more, thus 'Zone' options like

     Zone "example.com/IN"

are ignored if API version is 3.
bind plugin: split bind_xml_stats to v3 and v1_v2.

And minor change to bind_parse_generic_name_attr_value_list.
Merge remote-tracking branch 'github/pr/734'
Merge remote-tracking branch 'github/pr/697'
src/Makefile.am: Make sure plugins only export "module_register".

While there, put the LDFLAGS shared between all plugins into a separate
variable.
cpu plugin: Don't report empty cpu states.
feat(python-plugin): prepend instead of append ModulePath to sys.path

When importing a module, you expect the plugin repertory to have higher priority
than your site-packages. It will prevent hard to debug clashing module names problems.
At least, if there is a problem, it will fail more loudly than "module did not register
any config callback"
doc(collectd-python): update
Merge pull request #751 from ptbrowne/prepend-sys-path

feat(python-plugin): prepend instead of append ModulePath to sys.path