Merge pull request #57 from senseobservationsystems/temp_fix_proximity

Improved reliability and energy usage for proximity sensor
Changed data format for temperature sensor from JSON to FLOAT
Created relative humidity sensor
Added registration activity to demo app
Merge pull request #59 from senseobservationsystems/fix_sense_api_docs

Fix sense api docs
Merge pull request #61 from senseobservationsystems/fix_magnetic_field

Fix magnetic field
Update android support library to rev 13
Fixed Lint warnings about API levels
Deleted proguard config files (not used for library projects)
Added SenseApplication helper class to library, removed it from demo
project
Updated GCM library
Fixed name of rotation rate sensor in burst mode
Merge pull request #64 from senseobservationsystems/registration_demo

Added registration activity to demo app
Merge branch 'release-2.7.0' into unstable
Merge branch 'master' into unstable
Updated documentation with doxygen
Fixed reference to SenseApplication.java in demo registration activity.
fixed comment
Added opportunistic receiver
Opportunistic execution and backwards flexibility