Fix #27: When guessing sorting types, skip header

Always look at the first row of data when guessing the data type. If the
table doesn't have a <thead> element, assume that the first <tr> is a
header and skip it.
Fix #16: Recognized € as currency

- Recognize both "€5" and "5€"
- Also recognize if space in between: "€ 5", "5 €", "$5"
Keep 'no-sort' rows at their original position

Previously, rows tagged with 'no-sort' were pushed to the top of the
table when sorting:

  3
  2
  no-sort
  1

  =>

  no-sort
  1
  2
  3

Now, these rows are kept at their original position:

 =>

 1
 2
 no-sort
 3