Validate SP names for admin pages and REST
    
    We were previously only validating the SP name in the admin pages
    for SP creation and update.  The REST API would allow a SP to be
    created with an invalid name, which would break the ability to
    manage that SP in the admin pages.
    
    This patch moves the SP name validation logic out of the admin
    page code and centralizes it in the provider creation code.  This
    ensures that validation will occur regardless of the interface
    that is used.  In addition, a helper method is added to allow
    the admin page to check if a name is valid during update operations.
    
    https://fedorahosted.org/ipsilon/ticket/102
    
    Signed-off-by: Nathan Kinder <nkinder@redhat.com>
    Reviewed-by: Rob Crittenden <rcritten@redhat.com>