Removed maven build files
Changed project structure

Switched from custom layout to standard gradle project structure
Created core package for storing callback classes
Moved non-gui classes to 'core' package
Moved core classes into subproject
Fixed manifests
Check gpodnetEnabled() method before using gpodder.net API
Updated build files
Added more callbacks for SP
Added more changes to support SP
Added support for itunes:duration tag in feeds

Ported from AntennaPodSP
Updated config in app module, fixed typo
Set image owner when parsing feed
Merge branch 'migration' into develop

Non-GUI classes have been moved into the 'core' project in order to allow AntennaPod SP to reference it as a subproject.

Conflicts:
	app/src/main/AndroidManifest.xml
	build.gradle
	core/src/main/java/de/danoeh/antennapod/core/service/playback/PlaybackService.java
	core/src/main/java/de/danoeh/antennapod/core/syndication/namespace/NSSimpleChapters.java
	core/src/main/java/de/danoeh/antennapod/core/util/ChapterUtils.java
	gradle/wrapper/gradle-wrapper.properties
	pom.xml