Add full text search and create/update/delete on speaker - Jongo base

Add full text:
 - service : using new 2.6 API
 - UI in the home page
 - some information in the tutorial.html

Add CUD operation on speaker:
 - add the create/insert & update of a speaker : based on Jongo (to have a "model")
 - add the delete feature using MongoDB driver with the delete of the speaker in a talk (to see complex update) and delete of the speaker
No entry in the Tutorial (will discuss that later)