LP#2007877: various fixes to Server Admin Print Templates page

LP#2007877: various fixes to Server Admin Print Templates page

This patch fixes a regression introduced by the switch to NgbNav
as well as a number of other issues.

To test
-------
[1] Open the Server Administration -> Print Templates page and select
    a print template. Observe that the template editor is not displayed
    and that there are errors in the browser console.
[2] Apply the patch and repeat step 1. This time, the template is
    displayed along with its previewed.
[3] Switch to the Sample Data tab, then select another template. Observe
    that the template is reloaded and the active tab switched to the template
    editor.
[4] Select a template such as "Checkin" that does not have stock
    sample data. Observe that the Preview and Compiled Content panes on
    the template editor tab are empty and that the Sample Data tab
    has an empty control

Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>