Create shim Kohana_Exception_Starter for before modules are loaded

[yakatz]

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 #269

http://dev.kohanaframework.org/issues/4614

[enov]

@yakatz Thanks for this. This should have gone in 3.4/develop... but note that there has been some work done there to separate module definition and initialization.

See #530 and kohana/kohana#42.