Added support for qgcRebootRequired Fact meta data value.

It was broken when temperature translation was added in babbfbd1
The system wasn't quite setup to handle anything other than speed and distance. Changed so any arbitrary unit type can be converted to another.

It was broken when temperature translation was added in babbfbd1
The system wasn't quite setup to handle anything other than speed and distance. Changed so any arbitrary unit type can be converted to another.

Move  MAV_PARAM_TYPE to  MAV_PARAM_EXT_TYPE as we're now using the proper MAVLink version.

It did not like the use of the tr() macro within a static QString in the constructor.

Ignore Fact index if there are no enums (avoid adding an "Unknown" entry)
Add function to convert and clamp a (Fact) value.

Removed guess work from what parameters must be refreshed/updated when some other parameter changes. Added a "reset" flag that indicates when a certain parameter changes, the list must be reloaded.
Don't send a signal when setting a fact if the new value is the same.

Convert bool settings to SettingsFact

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

Fix knots to m/s conversion. Oops.