Be careful with QObject:::destroyed signal

Do not dynamic cast or de-reference QObject, since object is either in
destructor or may have already been destroyed.
Fix XPlane 9 operation, now tests ok. By Mark Whitehorn
Only reset if file is open
Use new QGCMessageBox apis

Subclass of QMessageBox which re-implements the static public
functions. There are two reasons for this:
1) The QMessageBox implementation on OSX does now show the title
string. This leads to message boxes which don't make much sense. So on
OSX we set title to text and text to informative text.
2) If parent is NULL, we set parent to MainWindow::instance. This
prevents message boxes which can go behind MainWindow
New File Locations key not set in QSettings at boot
Add Q_UNUSED to variable only used in Q_ASSERT

Should have known better!
Merge pull request #1003 from DonLakeFlyer/FixFileLocations

New File Locations key not set in QSettings at boot
Merge pull request #1002 from DonLakeFlyer/QGCMessageBox

QGCMessageBox implementation
Merge pull request #998 from DonLakeFlyer/Destroyed

Be careful with QObject:::destroyed signal
Rename files in git friendly way
File renames
Merge pull request #1006 from DonLakeFlyer/FileRenames

File renames
Commit
Remove unused
Track Singletons in QGCApplication

- allow unit tests to use QGCApplication
- clear global singletons for each unit test run
Mocks need QGCSingleton which does not register
Cleanup application object
Fix shutdown sequence
Merge pull request #1010 from DonLakeFlyer/Singleton

Singletons tracked by QGCApplication
Fix LinkManager link removal