[GSCKATA-34] Add new tests for aggregateBy api to Exercise 9

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[GSCKATA-35] Upgrade to GS Collections 4.0.

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[GSCKATA-35] Upgrade to GS Collections 4.0.

git-svn-id: svn+ssh://gsckata.svn.services.gs.com/svnroot/gsckata/branches/solutions@85 66aded80-052e-4344-91a8-38ab96726eea