Change when the sidebar is opened

Removed the show() call from showViewer().
Instead of this, I have manually added show() calls
to a few places. The result is this:

Don't automatically open the sidebar when
 * A new highlight is created
 * Heatmap is updated

But keep opening the sidebar when
 * Clicking on the heatmap
 * Clicking on a tab on the heatmap
 * Clicking on a highlight in the document

This closes #649.