Add useful examples and explain how to enable logging when an issue occurs
Add useful examples and explain how to enable logging when an issue occurs

git-svn-id: https://svn.apache.org/repos/asf/jmeter/trunk@1731945 13f79535-47bb-0310-9956-ffa450edef68

Former-commit-id: 21880c4e13983a1c11925dd28dbd5e4ea3847440
apache/jmeter,apache/jmeter,ham1/jmeter,etnetera/jmeter,benbenw/jmeter,apache/jmeter,apache/jmeter,benbenw/jmeter,ham1/jmeter,etnetera/jmeter,etnetera/jmeter,ham1/jmeter,ham1/jmeter,benbenw/jmeter,ham1/jmeter,benbenw/jmeter,etnetera/jmeter,etnetera/jmeter,apache/jmeter