[MATH-842] revert incomplete change and postpone.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1524213 13f79535-47bb-0310-9956-ffa450edef68
Qualify Evaluation in interfaces.

Use LeastSquaresProblem.Evaluation in the public interfaces for readability.
Expand Evaluation tests, use weighted values

Added more test cases to EvaluationTest to test the other methods of
DenseWeightedEvaluation/UnweightedEvaluation.

Fixed a bug in DenseWeightedEvaluation.computeValue() where the the weights were
not applied to the return value.
Merge with trunk.

It turns out I did a bad merge earlier that did not include some changes from
upstream. Now only the leastsquares2 packages are different from trunk.