Added KK2.1 target, fixed LCD test and added LED/timer test

- Added KK2.1 as target to Makefile. Target can be chosen by passing KKVER=2 or KKVER=2.1 to make. Default is KK2 board.
- Fixed LCD usage in kk2.c and added LED/timing test. The board LED will now blink on and off in one second intervals.
Added MPU support for KK21

- Added MPU6050 support from library.
- Created lib folder for third party libraries and modified Makefile to build them.
Delete kk2.c
Removed lcd folder since it's now in lib/
Merge pull request #1 from dankar/master

Added KK2.1 target, fixed LCD test and added LED/timer test