Add FullTextSessionFactory class which is exposed as a spring bean

Currently, the FullTextSession instances are obtained by calling LuceneQuery.getFullTextSession(), it would be nice and of great value to add an explicit Factory for these instances and expose it as a spring bean. One of the benefits of this change is it would allow a module to advise the spring bean and do some cool stuff before returning the FullTextSession instances.

One of the use cases for this, is so that a module can place the target full test session objects inside wrappers that will be returned so that it can enable filters on the targets in a single centralized place before returning them instead of doing it all over the code base which still leaves holes anyways.

Alternatively, FullTextSession should provide a mechanism to notify listeners whenever a new FullTextQuery object is created, so that they can do something extra stuff it e.g. enable/disable filters.

This should be a very simple change with no backwards compatibility issues, therefore, we can backport it to the 2.2.x branch.