Requirement ID Generation and RST Validation

Requirement ID Generation and RST Validation

The new check.py script will now perform a variety of
actions to simplify updates and ensure specific
practices are followed for each update.

The script has been integrated with tox and
will run whenever the documentation is created.
It can also be ran separately by just invoking
python check.py.

The script will perform a variety of automatic
updates where possible, and provide a warning
where auto-updates are not possible.

The expecation is that all warnings are addressed
before submitting for review, but given it is a
new feature warnings do not block validation at
this time.

Here is a summary of the warnings and updates:

Warnings:
- Requirement missing required attributes
- Invalid values for attributes
- Invalid section header usage in any file
- :keyword: and requirement mismatch

Auto Updates:
- Assigning :id: on new requirements where an ID missing
- Adding :introduced: attribute on new requirements
- Adding/correcting :updated: attribute on changed requirements

Issue-ID: VNFRQTS-896
Signed-off-by: Lovett, Trevor <trevor.lovett@att.com>
Change-Id: I283441330a139aa1c6e2e79f0c54c5979bf44642