better debug messaging for response to asynch 'blob:' request
ibid.
added error handling for file blob URL creation API that is unsupported by Safari
refactored for clarity
moved jslibs directory into js/
moved all 3 deliverable .js (and .json) files into new directory, '/js/json/' -- for clarity about *what* deliverables are.
moved all helper .js files into new '/js/jshelpers' directory.   (and finished normalizing /js hierarchy?)
altered references to moveed .js files