* Use global state instead of per-layout - so now window is minimized on
all workspaces (EWMH requires that windows with _NET_WM_STATE_HIDDEN
set should be minimized on any workspace but previously they were not)
* Use `windows` instead of `modify`. That should fix bugs related to
actions that should be done by `windows` and not done by
`modify` (fixes#46)
* Mark module X.H.RestoreMinimized as deprecated
