Added guard to abort when using the broken function -- to see what will break.
improved gradient descent in CNeuralNetwork
Adding "is_sorted" method to SGSparseVector for a better sanity check in "sparse_dot".
Added unit tests to detect sparse_dot bug.
Merge pull request #2134 from tklein23/broken_sgsparsevector_sparse_dot

Avoid broken sparse_dot in SGSparseVector - issue #2133
cleanups in CNeuralNetwork
Merge pull request #2135 from khalednasr/develop

improved gradient descent in NeuralNetwork
Reactivate unit tests.
Fixing sparse_dot() by checking if vectors are sorted (and using expensive fallback if not).
Minor style change.
Merge pull request #2137 from tklein23/fix_sgsparsevector_sparse_dot

Fix sgsparsevector sparse dot.