Send email form

__merge this after #7__

This PR add `SendEmailType` form type. It allow to send email to somebody. for this you have to go through several steps:

* select local
* select email template (templates filtered by locale)
* fill subject and body vars
* send email

It is not ready 

__UPDATE__

@jeremymarc @arnaud-lb  ready for use, implemented without tests. should I add?