Provide cache capacities on build process and ControllerListener 

The AdmingeneratorGeneratorBundle lacks of some performance issues on low performance disk access (for example: on network mounted drives).

This PR is just an import of some custom code used in some of my projects where I cache Admingenerator process repeated at each request (and using File Finder to identify which generator have to be used).

In my custom projects, I use "inheritance" mechanism to handle it. Here I try to find a way to introduce that feature without any BC Break.

 - [x] Writing some documentation
 - [x] Test developments

Because this is a new feature, it will be merged into a new Minor branch (1.2)

Work can be easily duplicated into your projects for 1.1 and 1.0 versions if needed.