Update playbooks_roles.rst

Fixes https://github.com/ansible/ansible/issues/7241
Removing hard coded link and replacing with reference
Fix the synopsis in ansible-pull man page.
Update playbooks_variables.rst

There is some kind of duplicated content with http://docs.ansible.com/faq.html#how-do-i-loop-over-a-list-of-hosts-in-a-group-inside-of-a-template and this gotcha isn't listed here.
Update developing_modules.rst
Updating Role class for new DataLoader stuff
Ignore compiled Python for documentation.

When running `ansible-doc --list` a lot of errors are
generated when `ansible-doc` tries to find documentation
strings in `.pyc` files.
Update playbooks_intro.rst

Small punctuation/grammar fix.
Merge pull request #9402 from mscherer/fix_man_ansible_pull

Fix the synopsis in ansible-pull man page.
Merge pull request #9410 from dannyroberts/patch-1

Update developing_modules.rst
Merge pull request #9422 from tonk/docfix

Ignore compiled Python for documentation.
Merge pull request #9425 from bobobox/patch-1

Typo fix in playbooks_intro.rst
Merge pull request #9216 from nmadhok/patch-3

Update playbooks_roles.rst
More v2 roles class work

* added ability to set parents (will be used when the deps are loaded)
* added role caching, so roles are not reloaded needlessly (and for
  use in detecting when roles have already been run)
* reworked the way metadata was stored - now individual attribute fields
  instead of a dictionary blob
added the ability to keep aliased and deprecated modules prefixed with
'_', they will be loaded after non prefixed modules are checked they can
be full modules or symlinks to existing ones (alias)

also updated ansible doc to ignore these, will eventually add selective
display
Adding role deps to v2 Role class and fixing some bugs
added fact caching hint
vars_files haven't been discussed yet

I think this is a chapter ordering thing... vars_files have not actually be explained yet (aside from a mention of them in the note right above, which also might need reconsidering?) I think they do get introduced in the next section 'Variables'.
module formatter skips modules with leading underscore to avoid
documenting them. Soon will be patched to recognize them as either
deprecated or an alias
added info about new deprecated/alias plugin loading