Add command for setting multiple icon overlays and workaround AppleEvent timeout issue with 10.8.2

- Workaround for AppleEvent timeout issue w/ OS X 10.8.2 described here: http://brian-webster.tumblr.com/post/32830692042/a-workaround-for-aesendmessage-hanging-on-os-x-10-8-2

- Add methods to set multiple icon overlays. Performance increases by one order of magnitude when looping through files in a folder.