Merge updates from Trunk
Merge documentation fixes.

* Use `doc/src/*.css` instead of `doc/html/*.css`.
* Remove wiki and people directories.
* Some documentation fixes.
* Left out `minimal.css` changes and boostbook changes because of clashes.
Merge more rebuilt documentation.
Merges patches from Trunk.
Spirit: merge from trunk, more to come
Merge bcp fixes from Trunk.
Fixes #5551.
Fix doc typo.
Merge minor fixes from Trunk.
Merge bcp fixes from Trunk.
Merge rebuilt bcp docs to release.
Merge fixes from Trunk: fixes GCC compile errors.
Merge doc formatting fix.
Fixes #8377.