Support new campaign structure (Do NOT merge before July 2nd!)

On July 2nd,  Facebook is (supposedly) fully migrating to a new campaign structure, going from a 2-tier to 3-tier setup.  This branch (which should not be merged until Facebook has actually migrated everyone over) adds support for ad campaign groups, which are the new 3rd tier of the structure.  Also, I added support for ad images, and creating credit lines for accounts.