First pack of changes in upcoming chain to redesign Rally docs.
All information related to Rally plugins separated and refactored.
Modified files fit 80 symbols margin where possible.
[TODO] continue with other parts of the docs:
- Contribute to Rally
- Request New Features
- Project Info
[TODO] add 80 symbols margin check similar to what
Performance Documentation has
Change-Id: I5d19a2bbbcdd9be463793bce50de62c5608b6157