Main concordance index should allow sorting by different columns

[rgrp]

Concordance index is a table with two columns: word, number of occurrences. Currently table is sorted by word but it would be nice to be able to sort by number of occurrences.

Implementation

1. For fun and instruction could use javascript to do this (use mochikit).

2. Alternatively just have another get/post option that allows one to specify sorting column.