Add domain entity editing functionality.

[ctrlaltdavid]

EntityServer API additions:

• canRez, canRezTemp, and canGetAndSetPrivateUserData domain permissions properties.
• canRezChanged, canRezTempChanged, and canGetAndSetPrivateUserDataChanged signals.
• addEntity() method.
  • Single packet. In progress.
  • Multiple packets.
• cloneEntity() method.
• editEntity() method.
  • Single packet.
  • Multiple packets.
• deleteEntity() method.
• getEntityType() method.
• entityExists() method.
• EntityErase packet handling.

Entity property changes:

• Add missing entity property, entityHostType.
• Fix entity property name angularDampling -> angularDamping.
• Fix entity property name cloneAvatarIdentity -> cloneAvatarEntity.
• Rename Model entity's animation properties: animation.animationURL -> animation.url, etc.
• Fix grab-related properties (grabbable, grabKinematic, ...) so that they are in a grab property group (same as native scripting API) rather than at root level and fixed up names.

Example app:

• Report domain permissions properties.
• Add, clone, edit, and delete example entity actions. In progress.