Add server-side attack support
Fix off-by-one error in path verification (the unit's current space counted)
Rename `unit.movesLeft` => `unit.moveLeft`
Add very simple client-side support for attack animation
Fix client-side unit-position dictionary bug
Fix misc attack and move bugs in UI
Fix pathing bug that allowed attack paths to end on an occupied space
Add unit health bars
Slight change to debug game info sent to server
Fix subpixel ugliness
When attacking, use previous adjacent path instead of computing new attack path
Fix variable name
Make health bars look less terrible
Fix client-side pathing bugs
Add attacks to right-hand display
Add function for future attack prompt code
Fix error message on impossible paths
Add terrain cover to pathing display