Added files

ADD Kinetis K60 headers
ADD Errors and types headers
EDIT includes in libohiboard.h
Added first release of UART Library
New library structure

- Use of opaque pointers for referencing the devices
- Hidden device implementation
- Added error signal as return from functions
Added header file of KL15 microcontroller.
Added support to the KL15 in the main file of the library.
Start to develop i2c interface.
Moved kinetis header file in a platforms directory.
Some fix.
Code refactoring of I2C device structure.
Added h file for Freedom board.
Manage all platforms with define.
Added system module for manage clock.
Some fix on define and include.
Added function for bus control.
Small fix in IIC name.
Another small fix in IIC name.
Static initialization of I2C on KL15 device.
Refactoring of define.
Merge branch 'origin/feature/i2c'