Updated config.yml and config_dev.yml

JSON, YML and XML views only in dev environment.
Updated pagination.html.twig

Page range changed to 3, href attribute in links only if != current page
Updated MessageBundle DataFixtures

Added CategoryFixture and using $this->addReference/getReference methods
Removed temp files
Updated getMessags.html.twig

Added pagination at the begin of the list
Updated web/app_dev.php

Using Xcache
Updated Message Entity

Added categories support
Added DateExtension Twig extension
Updated .gitignore
Updated Message entity : ManyToMany -> ManyToOne