First stab at Calendar day view sidebar

Summary: Ref T4393, First stab at Calendar day view sidebar

Test Plan: Open Calendar day view, sidebar should show today and the next 6 days, empty or not.

Reviewers: epriestley, Blessed Reviewers, chad

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T4393

Differential Revision: https://secure.phabricator.com/D12742