Bring old repository instructions and guidance forward to new UI
Summary:
Ref T10923. Fixes T10406. This brings most of the guidance/instructions forward:
- Some remained as instructions.
- Some moved to documentation.
Test Plan: Went through all of the sections and hit the help.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10406, T10923
Differential Revision: https://secure.phabricator.com/D15873