Add background page to store TUIServiceProvider Data

[andrew-smith]

Chrome plugins allow storing of data with localStorage - however that data is only accessible on the domain where it was saved. To overcome this chrome allows background pages that plugins can query and access a single localStorage instance.

We can use this to store the users preferred Service Provider (either twitter or identi.ca at this point). Functionality is in the plugin already but it does not use a single instance of the localStorage - each website has it's own instance.