WIP: Add FP2 support
To make this work on the FP2 I had to add a little bit of a hack witch commit 78ba8512 to be able to download TWRP from the official site.
There is one small problem: it seems like the installer doesn't immediately find the FP2 with adb devices -l.
Using the same command from a second terminal sees the FP2.
Eventually the installer picks up but I haven't debugged that further yet.