Everything is now based off of default font pixel size

Use default font wherever possible. Where that doesn’t work, use
ScreenTools::dpiAdjustPointSize.

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.

Tool bar buttons now use QGCButton as base to inherit hover mode fix.
Made QGCButton.showHightLight into a public property so I could use it as a trigger for repainting the chevron button.

Also realized I don’t need __lastMouseXY

Controls respect QGCPalette settings. Also added test window.