Remove unused imports and fields
medialibrary: Reuse the code for setting the dragged paths
medialibrary: Fix supported file formats lists
medialibrary: Use a local variable instead of a field for the error dialog box
medialibrary: Pythonic check
medialibrary: Allow importing MTS files
medialibrary: Pythonic iteration over supported file formats
medialibrary: Pythonic checks
medialibrary: Ignore all the uris which evaluate to False
medialibrary: Clarify the drag and drop handler
previewers: Do not fail if thumbnail timestamp is not the requested one

We should not miserably fail if the video thumbnail's timestamp is
not the exact requested one. Instead we try to figure out what the
timestamp means.
previewers: Optimize thumbnails reuse
previewers: Pythonic thumbnail time iteration
previewers: Implement TODO of using misc.quantize
misc: Rewrite binary_search and fix the test
previewers: Use the new binary_search method
previewers: Expect the keys method to return an iterable
previewers: Update comment about thumbnail time nanosecond precision
previewers: Reuse local variable
previewers: Consistent code format