Task #2061 - Lots of gallery UI fixes

Task #2061

It does the job, but I am not quite happy with the filtering code I just added in getMediaList() in GalleryFragment.java. It´s pretty ugly and inefficient. Thing is I need to filter out only media that has been tagged and media that has been shared.

Perhaps we could instead add these "sort" options to mediaManifest.sortBy() in the core?