Fixed some bugs in the form widget column sorting code:

1. URL parameters were being mangled by clunky string manipulation code.
2. The sort column logic was piggy-backed on the pagination event. I created a new choice for the form widget <on-event-update-area> element - "sort-column" - so column sort events can update their own areas.
3. The parameter name for the sort column was hard-coded, so column sorting in multiple lists on the same screen would not work. I added a new <form> attribute - "sort-field-parameter-name" - so each list can be sorted separately.


git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1488315 13f79535-47bb-0310-9956-ffa450edef68