Implement member management in camp

[NitayRabi]

Based on - https://app.zeplin.io/project/5c31adc4f5e7fcb018fbeef0/screen/5c58ae43451f6c422a13a936

Use existing MemberTable component under GroupManagement.
Split into 3 PRs -

1. Functional (show data - notice remarks on Zeplin).
2. Design
3. Implement adding member modal (see https://app.zeplin.io/project/5c31adc4f5e7fcb018fbeef0/screen/5c5f3288aa232e75540e4255 and all others under leader adds new members in Zeplin)

[NitayRabi]

Fixed by #77