Fix sorting in the issue summary table.

Review Request #9168 - Created Sept. 2, 2017 and submitted

Christian Hammond
Review Board

The issue summary table sorting code is really old, referencing the now
non-existent Issue ID column, and making some assumptions about content
and attributes of the rows that no longer apply. Sorting the Last
Updated field didn't work correctly at all, given that the cells no
longer have a timestamp attribute.

This change rewrites the entirety of the sorting code, fixing timestamp
sorting, improving performance, and adding support for sorting in
descending order (by shift-clicking columns).

Sorting has also been improved to sort by issue ID when two values are
equal, keeping the order of issues consistent when two timestamps or two
authors are the same.

Tested sorting all columns in ascending and descending order, and
verified that equal values fell back on issue IDs (always in ascending

Unit tests pass.

David Trowbridge
Christian Hammond
Review request changed

Status: Closed (submitted)

Change Summary:

Pushed to release-3.0.x (6dd12bb)