Utility classes

I've added a number of utility classes that I'd like to roll back into the main trunk. 

EnvPrinter - just prints the self.env array. Useful when debugging recipes. 
ScpUploader, SshCommandRunner - useful for maintaining your own (non-Munki) repository
PkgSigner - Digitally signs packages
FilePathElementsProvider - breaks out the file name, enclosing directory, filename without extension, and file extension
DateTimeTagger - renames a package to include a date/time stamp for versioning purposes
PkgInfoTemplateCreator - creates a PackageInfoTemplate file. I got tired of creating these things that only differ in the identifier attribute.