Replaced ImageLoader and DiskCache with Picasso

Implemented Picasso Downloaders

Replaced ImageLoader and DiskCache with Picasso

Removed ImageLoader, DiskCache code
Fixed NullPointerException in PicassoProvider
Use requestWindowFeature instead of support version

supportRequestWindowFeature throws a NullpointerException in some cases

closes #479
Increase maxLines in FeedItemDialog

closes #448
Abandon audio focus when a phone call comes in

Otherwise playback continues directly after the end of the call
Fixed typo
Prepared release of next version
Acquire wake lock when playing media
Acquire wifi lock if media file is being streamed
Removed FlattrConfig

API credentials have been moved into gradle.properties
Prevent flattr login if API keys are missing

closes #474
Merge branch 'issue-330' into develop
Pulled translations
Merge branch 'develop'