jMonkeyEngine: jMonkeyEngine 3.4.0-beta3

From jMonkeyEngine: link to the original post

A non-production release for development and testing, which will hopefully lead to a "stable" release.

Noteworthy changes relative to 3.4.0-beta2:

• Bugs addressed:
  • LWJGL context restart issues (PR #1526, issues #844 and #1445)
  • AnimEvent.onStop() kills prior event on the same Layer (PR #1537)
  • failed assertion in TestAnimMigration (issue #1533, PR #1534)
  • crashes in TransformTrack.getTranslations() and getRotations() (PR #1532)
  • jme3-jbullet depends on unavailable Maven artifacts (PR #1541)