Changer the way the rows are handled during sort

OK, so i had an issue with tablesorter losing the custom classes of my TDs when it recreates the whole table body, with whole new TRs and TDs.

What i changed :
- in bindTh(), we will now push the whole row to rowArr, instead of pushing an array with the contents of the cells
- I removed newRow() and newBody()
- replaced them with applySort(), which detaches all rows from the table and replaces them in order. Thus, all CSS/jquery metadata is kept.