Fix SIE stall caused by unhelpful Teensy usb_dev code

The original Teensy USB driver contained some code to helpfully clear any pending IN transactions when a new SETUP comes in. But this violates hardware's assumptions by messing with BDT entries from buffers that are still owned by hardware. Argh! This was causing the SIE to lock up while processing a SETUP immediately after a long control OUT transaction.
Additional DFU cleanup, usb reset callback
Enable watchdog timer
Whitespace cleanup
Start to specify the programmatic interface between bootloader and app
Tidy up teensy-specific wiring diagrams
Remove old tool for Teensy 3.0 bootloader
Rename legacy Teensy-specific firmware
Build firmware in DFU image format
Renaming to be less Teensy-centric
Header file cleanup
Trim startup sequence for FC-Boot apps
README updates, less Teensy-centric instructions
USB driver cleanup, and remove Teensy boot loader entry
Linker script for FC-Boot applications
Simplify linker script for FC-Boot, no more RAM IVT
Define OpenOCD scratch RAM area
Remove DFU USB Reset debugging
Turn off working RAM to work around another verify bug
More boot loader infrastructure

Having problems with the WDT though...