adding invitation app (sw_invitation)
return key on creation
app activation
invitation preview
include optionnal personnal text in the invitation email
Caution, translation block changed.
allow access to syndroms dict from other apps
dummy email for preview if no email is provided
using checkbox instead of radio to register into cohort
Merge remote-tracking branch 'origin/master' into italian-changes
Merge remote-tracking branch 'origin/feature-group-tracking' into italian-changes

Conflicts:
	templates/sw_cohort/form.html
	templates/sw_cohort/register.html
Merge remote-tracking branch 'origin/feature-invitation' into italian-changes
Locale update