Fix console warning in LegacyImmutableObject

It does check `hasOwnProperty`, but *after* accessing the field and therefore triggering enumerable getters in modified prototypes.
Add version to legacy factory monitoring
Don't transfer props to mocked empty component

We currently automatically render empty components in place of mocks. However,
we were accidentally transferring the props from the mocked descriptor to the
empty component placeholder. Even children.

This change just cleans that up and should only affect unit tests.
Start warning for JSX on plain functions

Let's also bump the version number for the log so that we can start filtering
out the other logs.
Bumping version to help filtering.
Bumping version to help filtering.