Camera Flags - Auto Exposure, Auto White Balance, & Raw Color

This enables toggling of a few camera flags.  Available flags are in the `freenect_flag` enum and values in `freenect_flag_value`.  Call freenect_set_flag() to enable or disable a flag.

Internally, hardware commands and register handling were split out into flags.h and flags.c.

Signed-off-by: Benn Snyder <benn.snyder@gmail.com>