Spaces inside organization names (GUI)

[stefan-contiu]

There is no indication that users can not create organization names containing spaces.

Can we add :

1. A short indication next to "Nom de l'organisation" saying the rules for the organization name? something like "letters and digits, no spaces"
2. Give an explicit error message if invalid characters are chosen by users. The error message today says only that name is invalid without an explicit information on why it is invalid.