Create shim Kohana_Exception_Starter for before modules are loaded

This will allow Kohana::$_path to be updated with all the module paths before they are used to load the real exception handler.
This (maybe) should be targeted to 3.4/develop, but that does not exist yet.

(This is working in production for me.)

Replaces https://github.com/kohana/core/pull/269

http://dev.kohanaframework.org/issues/4614