Initial bigip_node version
bigip_node: additional code

- checks if address already assigned to other node name
- add description for node
- check for node addres changes
- add missing code "node exists, potentially modify attributes"
Documentation additions and major refactor
Set default of 'yes' for update_cache, as is in the documentation
add docker module
add example docs
add python requirements to docs
clean up a few warnings
add requirements back
remove comment about requirements
Un-camelcase DockerContainers, rename class to DockerManager().
add a default value for the -d option of ansible-pull

Thi permit to simplify the command line to use by using
a sensible default, and so reduce the number of incorrect
possible choices and setup needed. Among potential
incorrect choices is using a fixed directory in /tmp, which
could be problematic with a setup whose access is not
properly restricted.
Fix a few minor issues in the Getting started document
Update intro_dynamic_inventory.rst

Minor fixes, style and typos
Update intro_adhoc.rst

Update link texts (hopefully got those correct from Sphinx documentation) and remove section on Limiting hosts as that's covered elsewhere
Move info on limit from the ad hoc command page to the pattern page
Update intro_configuration.rst

Minor RST fixes
Tiny RST link fix in modules documentation
Delete extra word in index.rst
Fixes #3847: lineinfile without regex