Extract method.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586401 13f79535-47bb-0310-9956-ffa450edef68
These methods can all be static.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586402 13f79535-47bb-0310-9956-ffa450edef68
Use the variable equivalent.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586408 13f79535-47bb-0310-9956-ffa450edef68
Extract another method.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586418 13f79535-47bb-0310-9956-ffa450edef68
Use isEmpty.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586428 13f79535-47bb-0310-9956-ffa450edef68
Extract method.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586429 13f79535-47bb-0310-9956-ffa450edef68
Slight simplification by abusing removeAll.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1586431 13f79535-47bb-0310-9956-ffa450edef68
Create PluginBuilder for Configuration objects.

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