Rationale: The concept of a "Qt Dir" is dead ever since Qt can be
installed. Specifying the qmake location otoh makes it possible to
unambigously detect all parts of a Qt installation.

- Give the controls a tooltip listing file details (date)
- Make building a QtConcurrent task
- Make log window scroll to bottom and pop up on error
- Make the build code pass on error messages about copying the
  source files to the log file
- Clean up the building code string-wise, use QLatin1String and
  translate messages, cache the icons. Use a QSharedPointer for
  the QtVersions in the settings page since they are passed to
  the BuildTask, which may outlive the dialog.

This reverts commit debb3961.
Success cannot be properly detected.

- Give the controls a tooltip listing file details (date)
- Make building a QtConcurrent task
- Make log window scroll to bottom and pop up on error
- Make the build code pass on error messages about copying the
  source files to the log file
- Clean up the building code string-wise, use QLatin1String and
  translate messages, cache the icons

Also, warn if no MSVC version could be detected even though the Qt
version was build with MSVC. This should make the tracing of problem
a bit easier. Before, we have hidden the GUI elements if only one
compiler version could be found. This looks inconsistent and causes
confusion.

After all I don't need all that stuff in the cmakeplugin, all i needed
is now bundled in debugginghelper.h/cpp

The Debugger, cmake and Qt4 plugin all need it. More refactoring to it
coming.

Reviewed-by: hjk <qtc-committer@nokia.com>

We used to build a helper library as part of the project. First with the
qmake -after SOURCES= stuff and after until now with the
gdbmacrosbuildstep. Now, the all new and fancy integretation directtly
into the qt version dialog. You build the debugger library once for
each qt version and then it's there ready to be loaded into each
project build against that qt version. Saves a lot of time.
And makes it possible to also load that library into while debuggign a
cmake project. (Need to hook that up now.)
Unfourtanetly this breaks the custom dumpers if you use a custom run
executable.