BLE: (+) Implement polling of the device for new values

(:) When the activity is stopped, the polling is disabled.
(:) When the activity is restarted, the polling is re-enabled.

Note that I have currently no idea on how to interpret the values
passed by the device.
Merge branch 'master' of https://github.com/glukas/DistributedSystemsProjects

Conflicts:
	workspace/VS_glukas_BleSensirion/bin/VS_glukas_BleSensirion.apk
	workspace/VS_glukas_BleSensirion/bin/classes.dex
	workspace/VS_glukas_BleSensirion/bin/resources.ap_