Fixed crash in FindUsages on a dirty file in a large project, which is saved
while the FindUsages is still running.

Reviewed-by: Erik Verbruggen

This uses the same UI as "Rename Symbol".
Moves the actual rename implementation to a static method in
BaseFileFind and uses it for rename symbol and search & replace.
Moves the signal notification for the code model from VCSManager to
the more general FileManager.
Note that as for rename symbol, there's no undo yet.

Task-number: QTCREATORBUG-73

Encapsulate the details.

Move the API to the progress manager.
Added a first Mac implementation, other
platforms are pending.

Ensure the code model receives file names with clean paths ('/')
and fix paths in the relevant places of the code model. Pass on clean
paths from Cpp reference find and display them correctly in the search
window tooltip.

Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>

Also fix focusing issues of the replace line edit.

Reviewed-by: Roberto Raggi

Unfortunately, the MacroResolver does not scale and we get pretty bad performances when parsing big projects.