Refactored timing of morse, wrote comments

all: All functions that measure time in morse ticks now use the
type ticks_t to reflect that we deal in morse ticks
rather than clock cycles or milliseconds.

key.h:
- The macro assignments that turn the morse pin on and off
now have their own macros MORSE_ON and MORSE_OFF.
- All spacings in morse now have their own macros defining
spaces in terms of morse ticks.
- Reversed order of arguments to macro EXTRACT_MORSE_BIT to reflect
the order of the pattern and length in morse_char_t.

key.c:
- The sendChar() should now handle spacing between characters
correctly without help.
- We now have charSpace(), wordSpace() and space() to deal with
all spaces in morse transmission.
Header file and #include cleanup

Cleaned up #include statements and header file stuff.