Since Ceres is moving to using GitHub for issues, and the Google
Code URL in the current copyright header will soon become invalid,
update all the headers.
Change-Id: I1fce70375d1bcf098591f07b4d8f01a5c1e0789c
1. Add the ability to evaluate the problem without loss function.
2. Remove static Evaluator::Evaluate
3. Refactor the common code from problem_test.cc and
evaluator_test.cc into evaluator_test_utils.cc
Change-Id: I1aa841580afe91d288fbb65288b0ffdd1e43e827