This is an alternative to MDL-17064.

Instead of specifying the number of fields in text area we could improve usability of repeat_elements function by adding blanks to the page without reloading, using Javascript (I beleive there is no need to use AJAX there).

Requirements:
1) silently fallback to current behavour if javascript is disabled
2) added blanks should have empty elements
3) user can delete unnecesary blanks (useful when you can't just find out if blank is empty, consider repeated <select> element)