Fix quizlet search by title and username requiring login

Conflicts:
	src/org/liberty/android/fantastischmemo/downloader/quizlet/QuizletSearchByTitleActivity.java
	src/org/liberty/android/fantastischmemo/downloader/quizlet/QuizletSearchByUsernameActivity.java
Fix Android 2.3 crasing issue.
Remove useless translations.
Update gradle version. Use different authority for pro version so it can install together with free version.