Removed init function in pio
Changed registers to struct in pio.h and changed all references to registers in pio.c and test_pio.c
Removed pio_close from pio.c and pio.h
Cleaned up the doxygen comments
Changed return in pio_read_pin from uint8 to uint32
Changed include to inttype.h in pio.h
CHanged brief descripttion of pio.h
Merge branch 'refactor_API' into refactor-pio
Merge branch 'refactor-pio' into refactor_API