Prevent table headings from scrolling out of view on collections index
table.

closes #2180
Move HeaderRowFixer out to application.js and application.css.scss

refs #2180
Output a blank line between pipeline status updates. closes #2182
Say when re-using existing jobs, even without debug mode. closes #2183
Merge branch 'master' into 2179-demo-feedback
Render collection provenance graph top-down like other graphs.

closes #2184
Merge branch '2179-demo-feedback'

refs #2179