Blat plugin fixes / enhancements (including Finder plugin fix)

Enhancements to Blat plugin documented here:
http://sourceforge.net/tracker/?func=detail&aid=3294976&group_id=27707&atid=391291

This includes a bug fix for the following reported issue:
https://sourceforge.net/tracker/index.php?func=detail&aid=2927805&group_id=27707&atid=391291

A prerequisite is fixing controller.js for Finder plugins as well in the
manner documented here:
http://sourceforge.net/tracker/index.php?func=detail&aid=3141696&group_id=27707&atid=391291