Upgraded Doxyfile to 1.8.7.
doc: make section names unique.
doc: specify ordering of sections in detailed documentation.

It makes sense, but this ordering also helps to avoid bug in Doxygen
1.8.6+ which merges next non-xrefitem section with the previous one (so
e.g. the TODO list contained the following @see block, which is not
desired).
Containers: completed documentation review.
Interconnect: completed documentation review.
PluginManager: completed documentation review.
TestSuite: completed documentation review.
Utility: completed documentation review.