Added caching of DB-Features (distinction between "request" and "get")
Added filtering of story-elements by poi- and tag-id (first steps for search-function) + Code improvements
Generating GoogleMaps-PolylineOptions out of stories
- added activity for story-elements
- database-handler is now global available
- many improvements between different acitvities
Merge remote-tracking branch 'origin/develop' into SpeechRecognition

Conflicts:
	app/src/main/java/de/ifgi/igiapp/igi_app/MapsActivity.java
Resolved merge conflicts