KeeperRL v1.0 hotfix 13 is out

The game won't show the upgrade button for workshop items that can't be upgraded.
General rendering and gameplay optimization thanks to Robin/Rob2309.
Fixed prison and pigsty rendering lag that was accidentally introduced during previous hot fixes.
Added support for Delete, Slash, Backslash, Semicolon, Page up and Page down keys in keybinding configuration, thanks to gnneo.