For https://github.com/turt2live/matrix-media-repo/issues/415

The new parameter `filterUserDuplicates` is set to true
everywhere else except in the import_synapse call. This
ensures direct duplicates from the same user will get
stored in an import from Synapse situation when migrating
to the mediarepo.

Closes #241

This should help memory some more. See https://github.com/turt2live/matrix-media-repo/issues/237

Theory is that by dumping the streams we'll relieve any bytes held on by the S3 libraries. 

Fixes https://github.com/turt2live/matrix-media-repo/issues/214

The script appears to work, just needed some touchups.

Fixes https://github.com/turt2live/matrix-media-repo/issues/93

Fixes https://github.com/turt2live/matrix-media-repo/issues/145

Fixes https://github.com/turt2live/matrix-media-repo/issues/187

Fixes https://github.com/turt2live/matrix-media-repo/issues/170

Part of #58

The middle layer is being completely replaced. We're keeping it for reference for now though.

Part of #58

This requires testing as per #93

Or on homeservers with only 1 record, the only media item.

Fixes #56

This is done over http to ensure that synapse is left with a backup of the media repository. 

Adds #4