Cli builder

I'm putting this PR out to solicit comments, please don't merge yet. 

This PR adds a new helper module that helps generate argument vectors for the aptly command. 
The motivation was to provide a reusable, easy way to mark which resource attributes were to be exported as command line flags when constructing aptly commands.

If you guys are cool with the approach I am taking here I will convert all of the objects to this style and begin filling in all the missing options.