Added Traderable interface to Transactions.
Players can now trade with Traders encountered in space.
Merge branch 'master' into sam/dev.

Conflicts:
	src/main/java/edu/gatech/gem5/game/controllers/DisplayUniverseController.java
	src/main/java/edu/gatech/gem5/game/controllers/EncounterController.java
last commit before pull from master.
Merge branch 'master' of https://github.com/gem-5/last-adventures into sam/dev
Traders now spawn with inventory goods that they can trade to the player.
Fixed UI bug, where trading with Trader was labelled as Planet.
Added trader.fxml file for TraderController
Bigger and better universes are here! Enjoy full panning and zooming action with incredible life-like immersion!
Some enhancements to the new universe display.
Major style update. Also added new star types to solar systems - update your save files!
Merge master into alex/dev

Conflicts:
	src/main/java/edu/gatech/gem5/game/controllers/PlanetController.java