jquery.tablesorter: buildCollationTable() on first sort, not on load

Since user and site scripts are now loaded after $.ready(), other
scripts may call .tablesorter() before they have done the
tableSorterCollation customizations.

Bug: 51982
Change-Id: I269181169a5e25fbd98eb2acbd9e2e0f45aaaa86
Merge "jquery.tablesorter: buildCollationTable() on first sort, not on load"