Patch various minor bugs

- "player clicks <item> in <inventory>" event will now fire
- fix rounding errors while animating chests
- gentler error when using the walk command on unspawned NPCs + also
auto_range better
Fix execute as_op

Slash at the beginning was messing things up... it worked when I tested
the commit adding the Preprocessing events, not sure what happened.
Merge pull request #742 from mcmonkey4eva/master

Pull request for minor things