Added checkbox to hide/show VMs based on current state

Looking at comments on pull request https://github.com/retspen/webvirtmgr/pull/326, I decided to try to implement the checkbox way.

I added a set of checkboxes over the filter input that let you hide all the VMs in that state.
It just hides/shows rows on the client side via Javascript, it uses data- attributes to match states by number to be localization friendly.