extension should load drives from the API

[gregwebs]

Currently Options.Authenticate is designed to load drives and other manifest data from a file ext_manifest.json at a gdocwiki installation

However, the extension should be usable without any knowledge of gdocwiki. The data being loaded

• drives: this can be loaded from the google drive apis (this is done in gdocwiki now)
• client tokens: this can be built into the extension
• domain: this can be gathered from the user's google identity