Tweaks to toolbar visibility

Re-architect toolbar for better customization capabilities. Also use less real estate.

Restructure toolbar to make it Flickable

Use showIndicator property to set correct visibility in loader. This leads to correct spacing on all platforms.

Handles branding logo visibility according to available space.

Windows fixes

Get rid of QGCView, QGCViewPanel and FactPanel. All messages and dialogs are now handled in the root window.

Other minor formatting and stability improvements

* Make MainToolbarIndicators reusable by other views
* Change to font based ratio sizing

* Vehicle selection must be global control
* Disconnect controls must be associated with Vehicle