Add Contractor to Secondary-Click Menu

We should find a way to add Contractor to the secondary-click menu for text throughout elementary OS. We had talked about specifically adding Lingo to that menu, but it'd be much better and more extensible to allow any service/app to tie into it through Contracts.

The contract would just have to accept plain text, then in the menu we'd have a "Share to..." menu item with a submenu of applicable services/apps. This would be an excellent way of using web services and apps like Lingo everywhere.