Smooth scrolling on focus change (worksheet list and worksheet details)
#665 keyboard nav fixes

- set a min-height on inline and markdown bundles so their focused state is apparent even if they're empty
- use the number of rendered .ws-item divs to set the max focus index in case something changed during render()
Merge pull request #667 from codalab/bugfix/665-keyboard-navigation

#665 keyboard nav fixes
Merge branch 'refs/heads/upstream/feature/worksheet_interface' into feature/561-edit-bundle-metadata