Use Qt::GlobalColor enum where possible.

The new values should be the same as the old values, no change intended.
Add setColors() helper function and cleanup header.

The new function is not used and no changes are intended with this commit.
Refactor dlgProfilePreferences.h/cpp.

Now there is less code duplication. This also fixes a bug where the 'set
colors to default' button didn't work for the map panel.