Fixing various output related things:

This was inspired by PR #4105.

* JavaScript output no longer requires calling container.show()
* Added output_javascript CSS class that has zero height when
  empty.
* JavaScript error messages are properly indented with the prompt
  area.
Merge pull request #4646 from ellisonbg/output-js

Fixing various output related things:

JavaScript output no longer requires calling container.show()
Added output_javascript CSS class that has zero height when empty.
JavaScript error messages are properly indented with the prompt area.