When the object is destroyed the connections will be removed
automatically by Qt.

fixes #433

fixes #418

This will remove some minor flickering (hopefully for good)

fixes #393

This was causing some flickering when many messages were added.
Mostly visible on macOS.

That's a fix to deal with long running sessions which will end
up taking more & more memory given enough time.

fixes #378

Add method to convert matrix content URIs to http links

fixes #215

fixes #351

fixes #346

Add missing megolm algorithm field that was causing
the "unknown algorithm" error.

Ignore devices that fail the verification.

fixes #345