Debugger: Rename Debugger:EngineType to Debugger:Type

Values "GDB", "LLDB", "CDB", the "Engine" prefix is a bit too
technical.

Change-Id: I81d97a435c796125015e8b7425e832420f338b9a
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
Tests: Fix tst_fileutils for Qt5.4+

Change-Id: I65b4eb8dff91c69bff50c63cd42a4894df0470f0
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>