initial
Merge branch 'master' into enhancer

Conflicts:
	.idea/workspace.xml
idea
Create AsyncTask for every map tile in order to not sequencially load the tiles
use default bitmap decoding settings as recommended by android
only invoke the enhancer when the bitmap is not null
don't add null values to cache
use the cached pool instead
use buffered reader
static executor does not make any sense
more null checks
don't always clear the file cache