Adding autoloading back to the Core->init function.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | -
| Fixed tickets | #899, probably also #883
| License       | MIT
| Doc PR        | -

Added registerAutoloaders method back to ModUtil and added a call to this method in lib/legacy/Zikula/Core->init.
Adding hooks to a modules works again after this update.
I can install News and add Scribite as a hook fine !