Merge pull request #43 from senseobservationsystems/unstable

Unstable
Added function to remove data before timestamp
Added functionality for storing 31 days of data locally and removing after that time
Now also taking into account available disk space
Documentation
Logging
Logging
fix sqlite thread lock
fix sqlite thread lock
Merge pull request #45 from senseobservationsystems/feature-KeepDataLocally

Feature keep data locally