Implemented the DAVERAGE(), DCOUNT(), DCOUNTA(), DMAX(), DMIN(), DPRODUCT(), DSTDEV(), DSTDEVP(), DSUM(), DVAR() and DVARP() Database functions git-svn-id: https://phpexcel.svn.codeplex.com/svn/trunk@68574 2327b42d-5241-43d6-9e2a-de5ac946f064
git-svn-id: https://phpexcel.svn.codeplex.com/svn/trunk@64719 2327b42d-5241-43d6-9e2a-de5ac946f064
git-svn-id: https://phpexcel.svn.codeplex.com/svn/trunk@59884 2327b42d-5241-43d6-9e2a-de5ac946f064