Also check for writable settings in unit test runes

Sorting source and headers while at it.

Initial rendering of Waypoints

- All resources are either under src or under resources dirs
- Removed files top level directory
- Move flightgear files to top level dir

If it doesn’t exist it will be prefilled with all registered categories
set to false

Created new ScreenTools exported control for QML code to obtain screen DPI factor to be used for computing font point sizes. This code used to be in the tool bar code and now is available to all QML widgets.
Moved global mouse position tool into ScreenTools as I felt it would be a place to collect these sort of functionality.
Replaced Tree used in the Safety Component from a PNG file to a SVG file as the PNG was not scaling up properly.

changed criticalMessageBoxOnMainThread(const QString& title, const QString& msg) to QGCMessageBox::warning

Shrunk the Message drop down dialog a bit.
Made the Message drop down dialog slightly transparent.

Replace QMessageBox::warning by QGCApplication::criticalMessageBoxOnMainThread and removed unnecessary copying action

Added to ". Please provide a different file name to save to." to the error dialog

changed QGCApplication::saveTempFlightDataLogOnMainThread(QString tempLogfile) to enable overwriting files
existing file is removed before saving file (QFile::copy cannot overwrite files)

The goal of this first installment is to organize the code a bit so it's more readable,
clean up a bit of left over cruft, and manage link configurations (and links in general).