Tried to order items in order of importance.
Also all perspectives now have their own shortcuts.

Both on the backend (replaced with DEFAULT view) and on the front end (removing UI menu items).

Includes removing an if-statement that should've been dead but was erronously applied to the following statement. Dead code = bad, if-statements without braces = bad.

This was deprecated on Febuary 3rd, 2014 and removed a little later. This finally completes that process.

Without this, when you go to airframe config and the current config is
Simulation it will not be selected. Hence you won’t know what the
current config is.

I don't think it's needed anywhere in QGC since this has been a bug for a long time.

SLUGS has maintained their patches out-of-tree for a long while now.
These will eventually get merged back in, but it'll be easier to evaluate them as fresh commits instead of modifications to this old & dead code, so we'll delete this for now.

Some functionality was lost, will need to be fixed in a later commit.

To include OpenGL primitives, we include the QtOpenGL header instead, which has all the platform-specific includes taken care of for us.

Also added selection from tree view for downloading