forward declaration is sufficient.

Details:  Adjust comments to actual situation

Details:  Now it even works for qtc's source.

Details:  That is we update all generated headers (which are new or
modfied) in the C++ Engine. Big if, this only works if we find the
correct path for the ui header files. Which is known to sometimes not
work, I'll fix that next.

RevBy: dt

Task:     Found by Roberto.

Details:  Free the whole ProFile*, ProItem*, ProValue* and etc
structure after parsing, that frees around 200Mb for projects.pro.

RevBy:    Patch by eskil
Details:  I can't really see why the path could be wrong there, and
can't reproduce the crash.

Task: 205821
RevBy: con
Details:  Add a IVersionControl to git. Extend IF to able to return a name and add enabling options. Connect project explorer to enable the right VCS.

Task:     Reported by eskil on irc.

Details:  ProFileCache be gone, as is ManagedProFile, not to be missed.
Drastically simplified how ownership works.