This guarantees we are past bootloader on all OS. Window tends to not
detect bootloader, connect to it and then get confused.

Windows OS doesn’t disconnect port when you pull plug on USB. This
caused all sorts of problems with previous logic. New logic handles
this correctly.

And other toolbar fixes...

Also reflow settings pane to take less space

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients