Kill no longer necessary PACKAGE_ID

:skull: death to old cruft.
Add support for easily adding additional search fields to the bottom of the search ui.

This could be ported to other commonly subclassed search indexes if it becomes widely useful.
Merge pull request #21 from isaacgrant/kill-package-id

Kill no longer necessary PACKAGE_ID
Merge pull request #22 from isaacgrant/additional-search-xml

Add support for easily adding additional search fields to the bottom of the search ui.