Copy NOTICE and LICENSE files to javadoc jar

This mojo (or ant build script) currently copies the NOTICE and LICENSE files to target/apidocs so that they are included in the generated -javadoc.jar. This is currently done in the commons-parent pom.xml using the antrun plugin. Doing it here removes the need to have ant script in commons-parent.

See:

• copy-javadoc-files.build.xml - Ant build script
• copy-javadoc-files.mojos.xml - mapping document
• Parameters