Expanded client sensors support.

Client now retrieves a list of all device sensors and
automatically registers/unregisters them.

See Issue 157. Corresponding server-side libsensors changes to follow.

Change-Id: Ia68a4d2ecb8840f9a0cae38d3de0baad27d46e79
Removed unnecessary NetIntents pieces

Change-Id: Ifd1ef783cac992112920ec74fa445c741f082ec1