create routes configuration
Doc to raise awareness of the Page Extras property.
Merge pull request #71 from symfony-cmf/create-route

[WIP] Create routes configuration
Fixed "decoupled CMS" link.
Merge pull request #73 from BilgeXA/patch-1

Fixed "decoupled CMS" link.
Merge pull request #72 from petesiss/extras-doc

SimpleCMSBundle Doc
minor tweak
added a note that SonataAdminBundle requires SecurityBundle