KNL-1242 Allow bean definitions to be overridden from sakai.home

When loading a Sakai component the loader will also look in sakai.home for a file name with the same name as the component plus an .xml extension and if present it will also load bean definitions from this file.

git-svn-id: https://source.sakaiproject.org/svn/kernel@315154 66ffb92e-73f9-0310-93c1-f5514f145a0a