Added function to get a list of the registered DataProducers under a name
Added function for getting registered DPs
Fixed unregister DataProducer unsubscribe processor. Remove key from list
Improved documentation, code style
Merge pull request #53 from senseobservationsystems/feature_getRegisteredDataProcessor

Feature get registered data processor
Merge branch 'release-2.7.0' into unstable
Converted ProximitySensor to PeriodicPollingSensor pattern
Made sure that PresureSensor unregisters the listener when stopping
sensing
Merge pull request #55 from senseobservationsystems/fix_proximity_unregistration

Converted ProximitySensor to PeriodicPollingSensor pattern