Split cam capture from compute step

components/rgbd-sources/include/ftl/rgbd/detail/source.hpp

components/rgbd-sources/include/ftl/rgbd/source.hpp

components/rgbd-sources/src/group.cpp

components/rgbd-sources/src/image.hpp

components/rgbd-sources/src/middlebury_source.cpp

components/rgbd-sources/src/middlebury_source.hpp

components/rgbd-sources/src/net.cpp

components/rgbd-sources/src/net.hpp

components/rgbd-sources/src/realsense_source.cpp

components/rgbd-sources/src/realsense_source.hpp

components/rgbd-sources/src/snapshot_source.hpp

components/rgbd-sources/src/source.cpp

components/rgbd-sources/src/stereovideo.cpp

components/rgbd-sources/src/stereovideo.hpp

components/rgbd-sources/src/streamer.cpp

components/rgbd-sources/test/source_unit.cpp