[orders] Adapt the order cart backend endpoint.
[comments/reviews] Adapt update commands.
[java-client] Refactor update command generation. Refactor comment/review update commands.
[cart] Adapt update action names.
[cart] Move createOrder() from cart service to order service.
Merge branch 'master' into futures

Conflicts:
	java-client/src/main/java/io/sphere/client/shop/model/CustomerUpdate.java
	java-client/src/test/scala/shop/CustomerServiceSpec.scala
	play-sdk/app/sphere/SphereClient.java
[futures] Adapt to Gregor's changes.
[futures] Use Play Promises in CurrentCart and CurrentCustomer.