[3.8] Add bin/setup doc, remove old commands

This is related to alchemy-fr/Phraseanet#333
This is V2 User manual starting point.
Add missing file
Few changes in Index.rst
no message
Minor changes
Fix Alternate text
Various fix in V2 user manual.
Various fix in V2 user manual (bis).
Add doc about bin/setup check:system exit codes
Remove "alternate text"
Cleanup first pass
fix build
second pass
Fix typo
Fix typo
Fix typo
Fix email/media
Addressed @nlegoff comments
Addressed @nlegoff comments