experimental: new file framework, allows content that is not a file
also fixes problems with adding multiple files with nested or multiple base files
fixed changes of 704199b9cb15a978f03ec2b468c2651d8a65e244 to work with android
minimal version is GingerBread now (API level 9)
android: test new file picker for all platforms (diffent intent)
android: support for kitkats new content system
android: re-enable direct file opening