Added endpoint that serves the timestamp/thread count pairs for all snapshots for a given day.  Reworked some of the filestore/snapshot code to make it cleaner and support grabbing that data.  Made a very rough first pass at actually graphing the data - still needs the proper hover detail labels, needs code to handle clicks on the graph translating to loading the given snapshot, etc etc.  Added a HTTP endpoint for pprof debugging at localhost:6060 when you run Cadastre with the --debug flag.