shimgen default output value (enhancement)

I was glad to see that you added the icon default value being the value of the icon of the target file (a couple months back now). I have a suggestion for the -o parameter as well if you want to add it. When the output parameter is not specified it should default to %CHOCOLATEYINSTALL%\bin\samenameasinputexe

Start by locating shimgen's handling of the -o parameter and how it determines the input executable and Chocolatey install path. The work is done when omitting -o produces an output at %CHOCOLATEYINSTALL%\bin\samenameasinputexe, with existing shimgen behavior still working.

Written by the indexing model from the issue text.