Remove more cruft from old project code
cosmetic: Bunch of extra newlines
Fix incoherent serial number between bootloader and other modes

Add a workaround for the serial number workaround introduced in
Teensyduino 1.19, related to a Mac OS X bug:
- https://github.com/PaulStoffregen/cores/commit/4d8a62cf65624d2dc1d861748a9bb2e90aaf194d
- http://forum.pjrc.com/threads/25482-Duplicate-usb-modem-number-HELP
Support Teensy 3.0 devices only by default

Add an EXPERIMENTAL flag in CMakeLists.txt, OFF by default, to enable
support for experimental features. Right now, disable models I haven't
tested.
Remove untested/broken support for mass storage device mode