This refactors the touchdocker to use qtquick controls.
I need to ask @leinir or @ahiemstra why exactly their old Button.qml does try to get the image from the IconImageProvider a few times, but when asking a QtQuickControls Button or regular Image to do so it only does so once(which is a bit annoying because it then only asks for an icon when the image size is 0x0 :/)
Anyway, this simplifies the code a bit.