DERBY-6680 Other jar files may need to be granted permission to read derby.ui.* properties

Patch derby-6680 adds a caveat to the template policy file to help
users avoid the issue seen by the user.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1618881 13f79535-47bb-0310-9956-ffa450edef68