Also fixes some resize issues with stupid workarounds to our resize
logic. This really needs to be cleaned up at some point!

This fixes some weirdness on some platforms, where Qt.openUrlExternally
does weird stuff.

This is necessary to support having a picker within QML.
Eventually, this should replace the existing widget-based one.

fixes #124

Quoted replies now include matrix.to links for the event and the user.
UI Rendering has been (slightly) improved... still very WIP.
Restructured the reply structure in the code for future usability
improvements.

fixes #215

* Refactor widget items to use same interface

* Support audio, video, generic file for pasting

* Add utils function for human readable file sizes

* Set correct MIME type for media messages

This change also determines the size of the upload once from the
ContentLengthHeader, rather than seeking the QIODevice and asking for
its size. This prevents any future trouble in case the QIODevice is
sequential (cannot be seeked). The MIME type is also determined at
upload once, rather than using the QIODevice and the underlying data
inside.

* Allow for file urls to be used as fall-back

This fixes an issue on macOS which uses `text/uri-list` for copying
files to the clipboard.

fixes #228 

fixes #132