Favorite trades select

Add the favorite trades dropdown menu.
Add pair action in menu.
Form defaults to the last favorite trade placed.

Fixes #761.

![output_nqfqme](https://cloud.githubusercontent.com/assets/3108007/4398511/87b6550e-4457-11e4-9767-a3fc4ba16fd6.gif)



Due to these changes, creating an offer for a favorite currency pair results in two separate wallet syncs.  Please change `moveFavoriteToTop` and `recordPriority` to not cause a sync, and then trigger a single sync from here.