Minor refactoring + suppport for intl. fox id

main.c:
- the sendFoxID funktion now supports the sending of
  fox id 1-5 (0-4) if the #define INTERNATIONAL_FOX_ID
  is present.
- All doxygen comments are now prefixed with '*' for multi-line comments
key.c
- sendChar() and sendLongBeep() now has the responsibility
  of both turning on and off keying.
- All doxygen comments are now prefixed with '*' for multi-line comments