Add email address field to organisations table

[spwoodcock]

Is your feature request related to a problem? Please describe.

• We still don't want a SMTP server ideally (using OSM messages).
• It would be useful to have a contact email for an organisation (previously we only link to a single user, but having an email means multiple users might access it (e.g. [email protected] might send to multiple people).

Describe the solution you'd like

• Add an email field to the organisation table. edit: done, added field associated_email
• Add a field to submit the email address during org creation (frontend).
• Save the email field in the db during org creation (update OrgIn schema to accept, backend).

Based on our discussion @manjitapandey