Add a calendar view for affect

[LeoMouyna]

According to https://docs.google.com/document/d/1-flXGzyOGWw6cMvHe6XFKJ_Gec2XE3_9XN9L9pNPvw4

We want to have a component with a calendar that show a user availability and tasks.

[LeoMouyna]

TODO:

• [x] Add a calendar view
• [x] Select a time slot
• [x] Assign to tasks
• [ ] Order displayed tasks
• [x] Unassign a user from a task
• [ ] Do back-end API's