Fix wlr 0.15 issues

[flaviozavan]

Fixes issues outlined in #78 :

• Broken Fullscreen
• Layer views not mapping
• Lack of XWayland restacking on focus
• Version bump

[inclement]

Seems to work great for me, thanks again

[inclement]

Oops, misread that it was merging into my branch rather than replacing it, will now merge the original PR too.