UART: Change comments
PID: Add tick timer

The tick timer runs at 1ms.
Init: Add motor module to module init function
UART: Change to 19200 baud
PID: Add motor channel freq. measurement timer

Rising/Falling edges on PORTE pin 0 will trigger a frequency measurement operation in TCE0.
Resulting CCA values are stored in an array that is used to generate an averaging filter.
Average is returned from the measureCCA function, and is updated every time CCA is changed.