Refactoring of headers and learn detail pages to support assay pages

- Made a first pass of a reusable header class, PageHeader
- Made a container, Page, that wraps a PageHeader and one or more child pages
- PageHeader supports tabs and renders tabs and switches between child pages in the Page that contains it
- Changed format of detail item data in cube.js to support arbitrary numbers of tabs per detail page
- Added some static data for testing Assay page with tabs
- Page header supports arbitrary locking height to support variable heights of interactive elements on different headers
Merge branch 'develop' of https://github.com/LabKey/cds into develop

Conflicts:
	webapp/production/Connector/app.js
	webapp/production/Connector/resources/Connector-all_01.css
	webapp/production/Connector/resources/Connector-all_02.css