Fix javadoc build on JDK 8
Fix javadoc build on JDK 8

This patch ensures the javadoc for GoodData CL tool is buildable on JDK 8.

gooddata/GoodData-CL,dagi/GoodData-CL,dagi/GoodData-CL,gooddata/GoodData-CL,dagi/GoodData-CL,gooddata/GoodData-CL