Tag rules based on URI

[Ninjani]

Would be handy to have a set of rules that automatically adds tags to pages from a certain domain. e.g a "paper" tag for publications from nature or any other journal, a "news" tag for news websites etc.

• Needs a file format to specify these rules
• Every gooseberry sync call needs to check new annotations against the set of rules and update them accordingly.

Note: I think it's important to prepend these tags with "gooseberry:" to keep them separate from user / other tools' tags and easier to search for.