introduce LocalTrack and RemoteTrack concept

DbAdapter is no longer used within Track. Track is a common object now.
include option to enable/disable debug logging; adjust some levels
fix unit tests after code restructure
move some local variables to static fields
move log statements
lazy load measurements on export/upload/map
decrease log level
automatically lazy load measurements on demand (strategy interface)
fix an issue when MainActivity is paused
enhance measurement management
fix NPE when activity was null (probably paused)
always access measurements via getMeasurements to ensure lazy loading
setting the default SDP uuid as the first candidate
new init overload, taking params for max time and space betwen measures
enhancements on DbAdapter impl (metadata mngnmt, active track resolving)
track creation IT
fix list view update on delete and upload of tracks
DNRY
Merge pull request #238 from matthesrieke/feature-reimpl-track-mngmnt

Feature reimpl track management