Players take damage when colliding with each other and blocks

If a player sprints into a wall or another player, they take a small amount of damage that armor can help with, but not eliminate. Also, make it so players can't sprint through each other as they can now. This will make pvp and running more realistic and less hectic. The same mechanics as elytra flight could be used for higher speeds (such as being fired from a TNT cannon or something).