Show restart dialog if update dialog is open

Change-Id: I8c160de7bb70692b99e1cd0bb3988666f3651db7
Reviewed-on: http://gerrit.dmdirc.com/2811
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>
Remove most singleton uses of WindowManager.

Change-Id: I1f054c7423106afe3fc49db8dc44613ec11c35bb
Depends-On: Idd97b752328310b4f829a45a43de5fdf6f5712a5
Reviewed-on: http://gerrit.dmdirc.com/2817
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>