Allow same gender selections

[sakshamsharma]

The current platform assumes that each person will be interested in people of the opposite gender. It would be better if the user is allowed to override this choice during signup time, so the user can choose whether he/she is interested in males or females (or both).

Requirements:

• The admin's /compute/prepare call needs to be modified to generate many more entries in the table.
• The user table needs to be given a new field for preference.
• The above field's value must be used by the frontend to fetch data (public keys, list of people, etc)
• The preference should not be public.