Zay-ES core version 1.2.1

Includes the new WatchedEntity support for tracking the components and changes for a single entity. There are other small internal infrastructure changes.

Additionally, this release is built with gradle and will eventually make it to a central repo... but the immediate benefit is that -sources and -javadoc jars are generated automatically and available as part of the release.

Changelog:

• Upgraded the project to be JDK 1.7 and source 1.7 based.
• Added the ability to get a WatchedEntity which acts like an entity
  except can be watched for changes in a way similar to a whole
  EntitySet. Useful for single-entity focused systems like player
  displays/controls.
• Deprecated the EntitySet.applyChanges(Set) method as it's not really
  possible to accurately return the changes that caused the set
  to be in its new state... especially not without a proper ordering.
  The network code that relies on this method has been reworked to
  do it more correctly.
• DefaultEntityData.getEntities() now delegates loading of the entities
  to the set instead of hand-rolling it. (The DefaultEntitySet was
  already capable of loading its own data.)
• DefaultEntitySet's Transaction.completeEntity() method was moved to
  the outer class so that subclasses can override how incomplete entities
  are resolved by the set.