Update bitstream-ordering.js

There is a bad JQuery selector in the following code. This causes a submit to take place each time an up or down arrow is clicked. It is difficult to see the error in the javascript console because the submit takes place immediately. 

Due to the page refresh delay, this is confusing to users when a large number of bitstreams are present. 

Note that "$^=" is not a valid selector. 

http://api.jquery.com/category/selectors/
Update bitstream-ordering.js

Found an additional scenario in which a javascript error occurs while re-ordering bitstreams.

Create an item with 3 original bitstreams.

Go to the edit bitstream screen and hit the down arrow on the second item.  An error will be thrown revealing a row without an id attribute.
Merge pull request #549 from terrywbrady/DS-2027

DS-2027 Update bitstream-ordering.js