Eliminate leading whitespaces when uploading new users from a file. 

In Users.php: uploadUsers function:
Added trim to eliminate leading whitespaces when uploading a series of
usernames.

Previously a file containing "Jim@mtus.edu, bill@mtsu.edu" would result in the usernames "Jim" and         " Bill" being added to the DB because of the space following the comma. This fixes the problem so that it does not matter if there is a space or not in the upload file.