* Allow multiple sources in each extension source apk
Minor code cleanup
* Add runtime defined sources functionality
* Undo extensions library major version number bump
* add local source
* small fixes
* change Chapter to SChapter and and Manga to SManga in ChapterRecognition.
Use ChapterRecognition.parseChapterNumber() to recognize chapter numbers.
* use thread poll
* update isImage()
* add isImage() function to DiskUtil
* improve cover handling
* Support external SD cards
* use R.string.app_name as root folder name