wldhx

I'd thought that we would initially just add targets like `flash.stlink` to existing makefiles, and then perhaps check if users' Makefiles have something like `PROGRAMMER = stlink` in them to...

For reference, I'm still on this; it's just that I had a loooong break from all things embedded :) I think I'll change #20 a bit to include "basic" programming,...

@brghena, @bradjc I think I'm more or less done - could you review?