Order backend 3 - FriendlyOffers

This PR adds the concept of a FriendlyOffer, that is, an offer that is expressed as a buy/sell operation according to the current users preference.  An example usage is provided on the trade page that shows these friendly offers in the "My Offers" section.

Additionally, we also move the concept of a "live" order book into the OrderBook service itself.  This is in preparation for live updating order books, which should be landing shortly.