Add Schema for Groups aka Squads, Houses

[punitrathore]

Squads in Echo

• As a admin or staff, I should be able to create a "SQUAD", which is a list of members, and has a leader.
• As a member, I should be able to see which squad I belong to.
• As an admin or staff, I should be able to see the squads for which I'm a leader.
• As an admin or staff, I should be able to add/remove members of the squad.
• As a member of a squad, I should be able to see all the other members of my squad.
• As an admin or staff, I should be able to see the status of workplans and retros for each member of the squad.

Schema Details:

groups:

• type (squad|house)
• leader-id
• name

member-groups:

• member-id
• group-id

members: (already implemented)