FEATURE: getFirst/getOnly now use UtilValidate to verify non-emptiness.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1482004 13f79535-47bb-0310-9956-ffa450edef68
FEATURE: Add getFirst/getOnly variants that take a collection.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1482005 13f79535-47bb-0310-9956-ffa450edef68