Replace Indirect Wiki pages with RST files using the interface directive

[DanNixon]

This ticket is blocked by :

• TRAC10863

This ticket is blocks : TRAC10960

The Wiki pages for indirect are far from perfect and a pain to keep up to date, since there is some nice functionality for making custom interface documentation in the same way as algorithms, etc. this should be used instead, especially since this means the documentation will be available offline.

Links to the new help pages should be added on the current Wiki pages and the "?" buttons on the interfaces replaced to open the Qt help.

[DanNixon]

This issue was originally trac ticket 10711