Convert bool settings to SettingsFact

* Holds all the settings for the app
* Allows core plugin to override default values

Use component id from heartbeat

Allow plugin to define default font size, toolbar height and option to display/hide plan view selector.

- Shot Interval in Survey
- Much change to time/distance calc

This makes text show up better on map images

Prevent shutdown ordering crashes

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

Shows horizontal/vertical scroll indicators

Made QGCCorePlugin derive from QGCToolBox and expose everything through the same mechanism as everything else.