Find a way to register new PHP callbacks in XSL templates

Postponed until ticket #40 is resolved.

This ticket requires ticket #80 to be resolved.

Fixed with changeset 878.

To configure the callbacks used within the XML/XSL post processor the file config/xsl-callbacks.ini needs to be edited. One line denotes one callback where the key is the id with which the callback may be called from within the XSL template while the value references the full qualified class name of the class which contains the callback method to be called for this callback. The XML/XSL post processor now required that in instance of net.stubbles.ioc.stubBinder is available in the registry under the key net.stubbles.ioc.stubBinder. If the ini file or this instance is missing the post interceptor will throw a stubException during runtime.

When adding classes to the ini file that have dependencies on other classes which needs to be injected into the desired class these dependencies should be configured in the stubBinder instance within a separate pre or post interceptor.