help: remove reference to right-click popup from medialibrary.page
- removed /figures/previewsource.png
- removed also from Makefile.am
help: remove the Typeahead search section from medialibrary.page
help: update the View modes section in medialibrary.page
help: add the Importing a file section to medialibrary.page
help: add the Other actions section to medialibrary.page
help: update meta info in medialibrary.page