Add package manager detection to Test::Pkg

[agjohnson]

Test::Pkg should attempt to set the default package manager, so explicit configuration isn't required. This can be fairly accurately by detecting OS and then Linux distribution. Distribution package managers will need to be explicitly defined however.

[agjohnson]

Instead of performing distribution check in Test, and providing abstraction for separate package names, export util function to base, for direct use in scripts.

Edit: nevermind, putting this functionality in the test works well