add update school registration data to the USSD menu as a further option on post initial registration

This is for recognised MSISDN's only. Updated menu should now be (Note changed intro too.):

> What would you like to do? 
> 1. Report on teacher performance 
> 2. Report on learner performance 
> 3. Change my school 
> 4. Update my school’s registration data

Selecting 4 should drop into a new choice state `manage_update_school_data`. Text:

> You'll now be asked to re-enter key school details to ensure the records are accurate. Enter 1 to continue:
> 
> 1. Continue

Selected 1 should drop into the new `reg_school_boys` state. The self.cms_registration function will need updating to look at initial_state to see what the user was trying to do.