LP#1516867 Make HTML report tables sortable

LP#1516867 Make HTML report tables sortable

Using the sortable JavaScript library from https://github.com/hubspot/sortable
(MIT license), we can make HTML reports much more usable by making them
sortable by clicking on the column headers. This should save some downloading
of CSV or Excel versions of the reports.

To test:

[1] Create or use a report template and generate an HTML report; ensure
    that the report has at most 10,000 rows of output.
[2] View the report output and click on one of the column headings;
    verify that the table sorts itself by that column's values.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Ben Shum <ben@evergreener.net>