charm: add BundleData, parser and Verify method.

This is the start of the bundle specification discussed at https://docs.google.com/document/d/1SF8hTBi6oVbki8V__beNij6wnQU-5cm6PZsy5gf0j_Y
So this is saying to place it on 'machine 0' which in this case is the one mediawiki is created on, and mediawiki/0 which is the first unit of mediawiki? Are both specifying the same thing really. The location of mediawiki/0 will be machine 0? 

What about just

    to: mediawiki
    to: mediawiki/2