Provide better headers and crumbs for Calendar result views

Summary:
Ref T11326. This isn't perfect, but should be a little easier to use and less weird/confusing.

Generally, provide a "Query > Month > Day" crumb on day views, and a "Wed, July 3" header.

Generally, provide a "Query > Month" crumb on month views, and a "July 2019" header.

Also try to fix a bit of padding/spacing on the day view.

Test Plan:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11326

Differential Revision: https://secure.phabricator.com/D16338