fusion: merge of associative iterators/views and the new fold interface
Copy generated fusion documentation from trunk.
merge from trunk
merge from trunk
merge from trunk
fix #1614
removes outdated and defunct files
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.
merged revision 62675
merged fusion from the trunk
merged fusion from the trunk (2)
Merge rebuilt fusion documentation.
Spirit: merging from trunk upto rev. 61347
Merge rebuilt fusion documentation with missing file.
merged fusion from the trunk (3)
fix for adapted classes' category
Fusion: merge from trunk
Fusion: merge from trunk
Fusion: merge from trunk - fixed minor doc typos
Merge units from trunk