Revert "loading plugins after user scripts are parsed so that plugin initializers may reference user event handlers"

This reverts commit 169efe86443c463d4cabe5d7cfeeb81f9642b562.
Revert "Revert "loading plugins after user scripts are parsed so that plugin initializers may reference user event handlers""

This reverts commit 77e900aafb4865c0fdbef8cde6fb1686becbdf0c.