freertos: remove useless default_handlers.o
remove deprecated tower test apps, create new test apps,
change cabal dependencies to new tower 0.8
ivory-bsp: comment out nonworking modules
ivory-bsp-stm32f4: tower signals implemented properly

* template haskell builder for Signalable instance of a platform type
* STM32F4Signal class gives a platform SignalType from an STM32F4.Interrupt
build fixup - spelled tower-example-stm32f4signals wrong
ivory-bsp-stm32f4: correct implementation of UART.Tower
ivory-bsp-tests: bsp-uart-test now works (tests UART.Tower)
ivory-px4-hardware: px4ioar driver works with tower-statemachine

great victory
ivory-px4-hw: remaining code fixed for tower 0.8
ivory-bsp-stm32f4: use channel' instead of channelWithSize
apps - disable bsp spi test (broken, wont fix soon)
flight: port to tower 0.8 api. compiles, runs, not thoroughly tested

* ardrone motor driver not 100%, sometimes it fails to boot, suspect the
  new timing properties of the uart driver is responsible for this.
* stack sizes may not be correct quite yet
ivory-bsp-stm32f4: import ATIM18 lib written for tower-examples
ivory-px4-hw - fix timing in AR Drone motor initialization
flight: correctly initialize ITime period for stream initial rates
ivory-bsp-stm32f4: uart driver implementation fixes
ivory-bsp-stm32f4: add register names as strings
ivory-bsp-tests: created "stress test" of uart timing for open407 board

seems to fail after a little bit on uart2
will investigate more tomorrow
ivory-bsp-stm32f4: add interrupt set/clear pending to api

* didn't help my problem, but they were pretty mechanical to add