Resolves #111 with source capabilities

applications/gui/src/camera.cpp

applications/reconstruct/src/virtual_source.cpp

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

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

components/rgbd-sources/src/middlebury_source.cpp

components/rgbd-sources/src/net.cpp

components/rgbd-sources/src/realsense_source.cpp

components/rgbd-sources/src/source.cpp

components/rgbd-sources/src/stereovideo.cpp

components/rgbd-sources/src/streamer.cpp