Minimize dependencies of artdaq-core
We should provide the mechanisms for analyzing artdaq data files in gallery. This originally was to take the form of moving artdaq::Fragment into a separate package, but it was determined that we would still need art-independent dictionary files. Therefore, the decision was made to push artdaq_core's dependency on art down to canvas, so that it can be included in projects using either art or gallery. artdaq itself now includes art for running DAQ.