User creation by Non-Admins

[danielfdsilva]

Right now the user creation is reserved to the admins.
There are no role differentiation when creating users so, anyone with the correct permission, can create/edit any type of users (including more admins).

This poses a problem because every time a call center agent needs to be created or a password needs to be reset, an administrator must be contacted.
It's not an option to give the 'create users' permission to moderator since they could promote themselves to administrator.

The user creation process should be revised in order to allow moderators to add agents.

Maybe add some kind of configurable permission on what kind of users each role can create?