Document cookie null value handing; also update httpclient URLs
Document cookie null value handing; also update httpclient URLs

git-svn-id: https://svn.apache.org/repos/asf/jakarta/jmeter/branches/rel-2-2@574055 13f79535-47bb-0310-9956-ffa450edef68

Former-commit-id: 802e3dceda899abf235deef325c880bcbc1bb5f9
ham1/jmeter,apache/jmeter,apache/jmeter,apache/jmeter,benbenw/jmeter,ham1/jmeter,ham1/jmeter,etnetera/jmeter,benbenw/jmeter,apache/jmeter,etnetera/jmeter,ham1/jmeter,etnetera/jmeter,benbenw/jmeter,ham1/jmeter,benbenw/jmeter,apache/jmeter,etnetera/jmeter,etnetera/jmeter