PCA9685.h: add externs for MODE1 and MODE2, define all bits
PCA9685.c: assign hardware defaults to MODE1 and MODE2,
in initPWM, always set AUTOINC and always clear SLEEP, EXTCLK, and RESET,
and always set MODE2, remove #ifdefs
PCA9685demo.c: add opts for configuring MODE1 and MODE2,
add -h usage message and -V version number
PCA9685.h: add externs for MODE1 and MODE2, define all bits PCA9685.c: assign hardware defaults to MODE1 and MODE2, in initPWM, always set AUTOINC and always clear SLEEP, EXTCLK, and RESET, and always set MODE2, remove #ifdefs PCA9685demo.c: add opts for configuring MODE1 and MODE2, add -h usage message and -V version number