added linear responsiveness fro the entity's def.
fixed an issue with mesh creation.

When you created a mesh instance, the `renderingGroupId` of the parent and all child meshes was reset to 0.
fixed sending events

Sending events were broken, because they didn't have 'event' on the front. Simply used the wrong variable...
fixed setting of target velocity.
send input events when commands are triggered.
implemented handling of updates.