Removing old protobuf files before starting a new build.
Merge pull request #2223 from tklein23/remove_old_protobuf_files_before_build

Removing old protobuf files before starting a new build.
reduced accuracy in kernel row_col_wise_sum_block_with_diag unit-test to prevent buildbot failure
Merge pull request #2224 from lambday/develop

reduced accuracy in kernel row_col_wise_sum_block_with_diag unit-test to prevent buildbot failure
added opencv as the optional dependency and a basic test in tests/integration/opencv.
added flags for opencv integration in CMakeLists.txt.
shortened the flag name for OpenCV integration
opencv integration test cleaned_.
removed system include for OpenCV from CMakeLists.txt