Upgrade jQuery tokenInput plugin to 1.6.0

I found that I needed the tokenFormatter and resultsFormatter callback options available in tokenInput plugin version 1.6.0, so I upgraded to that version. The attached patch upgrades the file to 1.6.0.

Note that the current version 1.5.0 plugin as it is in CiviCRM differs in a few important ways from the plugin author's publicly distributed plugin file, and those important differences are maintained in this patch.