Many links are broken or point to redirect pages, update all of them.
Use better RST for intra-document links so that they do not silently
break if documents move.
Use opendev.org consistently for git.
Change-Id: I8fedff2fff82177fd12da808b8b421270cbe2d95
The legacy install-guide directory is removed, projects
host thei install-guide under /doc/source/install/.
It should have been done in:
Ifdeb7c669e7f2351aff837f43f2fa3515a89e086
Change-Id: Ia65804cd01ada25f6b61c1c4bcb246d5a4c9c570