Tree Model 2 Electric Boogaloo

This draws heavily on what @carlschwan did in network/neochat!1579 but I found it easier to start again and grab the bits as I needed them plus some other copying from what I did in the Space tree model.

From my current limited testing this seems to work nicely try and break it.

src/CMakeLists.txt

@@ -172,6 +172,8 @@ add_library(neochat STATIC
     models/statekeysmodel.h
     sharehandler.cpp
     sharehandler.h
+    models/roomtreeitem.cpp
+    models/roomtreeitem.h
 )
 
 set_source_files_properties(qml/OsmLocationPlugin.qml PROPERTIES