Disable all debug output by default.

If you need to enable additional logging for debugging use a rules
file as explained in the QLoggingCategory documentation:

http://qt-project.org/doc/qt-5/qloggingcategory.html#logging-rules

Also possible is to set the QT_LOGGING_RULES environment variable
temporarily, e.g.:

QT_LOGGING_RULES=kdevplatform.project.debug=true kdevelop -s ...
-> you'll see project debug output again!
Use kdevelop.definesandincludes as logging category for IDAIM.
Cleanup code and fix signal signature.
Fix assertion about unknown projects in the IDAIM.

The problem was that projects opened before the IDAIM plugin gets
initialized where never added.

To add these in the ctor (synchronously! otherwise we get races),
we must restructure the code a bit. It is notoriously overdesigned
and really should be simplified. Why is the CompilerProvider a plugin?
Why is there ICompilerProvider? Why the distinction across so many
libs/plugins?

Well, more work for later.
Re-enable the cmakecompletionmodel
Bring the cmakedocumentation plugin back