storage: make filenames provide some info; make updating cache a little more robust
storage: make filenames provide some info; make updating cache a little more robust

DrXyzzy/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc,sagemathinc/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,DrXyzzy/smc