Wax update to 0.8.3

This looks like a wild number of changes, but it's just updating Wax to the latest version. Wax modules were split across five different packages; now they're two packages, so a lot of imports changed. Everything is now coming from either wax-prosemirror-core or wax-prosemirror-services. Also the Prosemirror packages were updated to the versions that Wax is using internally.

This was not working until I moved all the prosemirror packages into resolutions in package.json. Christos says we should not have to do this; maybe this will change in a future Wax version, though hopefully that upgrade won't be so complicated!