SiO2 release 1.0.3

An incremental release with the following changes:

• Flipped the GameLoop's update loop to sleep when idle instead of
  only after an actual update was run.
• Modified GameLoop to allow configuring the amount of time to sleep
  when idle-busy-polling for the next update interval.
• Modified GameSystemManager to log its update errors before sending
  them to the event bus as a fatal error.
• Modified the EventBus to log.debug() any events that are undelivered.
• Modified the build.gradle to replace the JME version with a specific
  version instead of letting it float. I think alpha4 is generally
  the minimum accepted 3.1 version at this point.
  Did the same for all of the floating version references.