Robustly upgrade, install, or uninstall ansicon machine-wide

I hope you like where I'm going with this pull request... 

 * reduce complexity with regex matching, guard clauses, and functions
 * accurately model the ansicon autorun property
 * reliably update and even uninstall the autorun property

I don't know if you ever solved the problem of overwriting the ansicon files on upgrade or removing them on uninstall. I don't have an answer yet, but I wanted to get this in front of you. I think `cmd /D` might be the answer somehow... http://technet.microsoft.com/en-us/library/cc779439(v=WS.10).aspx