added serial mouse driver for Microsoft and Mousesystems mice

 * Both drivers use the interface defined in serial_mouse.h
 * They should work with any UART implementation (hardware/software UART)
 * The Microsoft driver is currently untested.
   The Mousesystems driver is confirmed to work.
fixed PS/2 keyboard converter config

When using the PS/2 interrupt implementation, the DATA pin should be
PD0 as the documentation (README.md) states.
integrated serial mouse drivers as a feature into the firmware architecture

 * can be enabled by defining Makefile macro SERIAL_MOUSE_MICROSOFT_ENABLE or
   SERIAL_MOUSE_MOUSESYSTEMS_ENABLE.
 * Serial implementation can be chosen via SERIAL_MOUSE_USE_SOFT and
   SERIAL_MOUSE_USE_UART macros
 * UART configuration still has to be done in config.h: I added working clauses
   for both mouse protocols to ps2_usb's config.h
factored out serial_mouse_init() into serial_mouse.h
serial_mouse: simplified clipping of X/Y/V/H changes below -127 using a MAX macro
updated copyrights: serial_mouse.h, serial_mouse_microsoft.c and serial_mouse_mousesystems.c are new
Merge branch 'serial-mouse' of git://github.com/rhaberkorn/tmk_keyboard into rhaberkorn-serial-mouse
Revert ps2_usb/Makefile and config.h
Revert lufa/lufa.c
Add serial_mouse_task in keyboard.c
Add option 7bit data to serial_soft.c
Add serialmouser_usb project
Merge branch 'rhaberkorn-serial-mouse'