Catkinised phidgets_drivers metapackage

Catkinised phidgets_drivers metapackage.

Successfully compiled under ROS Groovy and Hydro.
Successfully tested with Phidgets IMU 1056_0.

Notes:
Source code has not been modified.
Added new header file -- phidget21.h -- to phidgets_api, and modified include path to phidget21.h in phidgets_api/phidget.h.