Standard buttons are ordered in the right way and sometimes have an
icon.

Bug: https://matrix.to/#/%23nheko%3Anheko.im/%2476PZ2m6YftX8mqGIe9ettKbh_-pEYeVRQSJBfwFzWi0?via=pixie.town&via=matrix.org&via=matrix.flexinos.tech&via=half-shot.uk

Allows you to zoom and pan now.

relates to #647

This ports the leave room dialog to QML, everywhere. There are now no differences between the various leave dialogs.

Using a dialog after username and password have been provided.

There are probably a few things wrong with this, but I'm going to call it good enough for an initial commit

This also adds a property `roomId` to TimelineModel.