Enhance meta-docs on... contributing to docs.

- Update FAQ entry to refer to docsite README and reduce redundancy.

- Add additional info to docsite README: Sphinx building, link to module
  documentation reference.
Add raw copy support (raw=yes), tweak tempfile error message string.
Fixup error reporting.
Fix prev feature commit, Do not require aptitude to use apt commands in the apt module, only needed when upgrading.
Fix to group_by module as a result of previous conditional upgrades.
use global to fail as its not in self
Signed-off-by: Brian Coca <briancoca+dev@gmail.com>
also rename plugin name in error message
Continue on mount errors, don't fail the setup module.
Minor cleanup of YAML Syntax documentation
Replacement for apt_repository.
1. Debian Squeeze is supported out of box now.
2. Repository type "deb" or "deb-src" should be explicitly specified.
3. If a source had beed added it must be possible to remove it.
4. PPA can be only used against Ubuntu hosts.