Shortcut names for different environments

[RichardSinden]

This adds a preferPackageName flag for shortcut creation and removal, to allow for situations where you want to use the package name in preference to the executable product name. e.g. repackaging same assembly with different config file for different environments. Resolves #164

I made the change in master because I needed a working build, but I can also merge into the develop branch if you're happy with it.

[caesay]

In general, Squirrel expects apps to handle creating shortcuts themselves - and provides a helper method to do so. It would have been more sensible to add just an overload to that one method CreateShortcutsForExecutable (instead of every method related to installing and updating).

There are a few reasons why this is not necessary, and as it is a breaking change I won't be accepting it:

• It's possible to create the shortcut yourself already using ShellLink class and avoid the Squirrel methods.
• You can update your exe product name after builds using rcedit so that Squirrel will pick this up automatically