KLxx refactoring

Bringing the code of all KLxxZ devices to a single code base, with some target specific files. 

Other change is that the option to set 9/10 bit UART transmissions is removed: The code to set the correct registers was there, but the actual write and read code only did 8-bit. Someone else can properly implement that ;)

See also: https://groups.google.com/forum/#!topic/mbed-devel/pNlC6OdJXKo