some debugging utils in webserver; fix JSON encoding.

In summary:
  1. Fix the JSON encoding issue (unescaped quotes, _etc_); The json2mat may still be broken.
  1. Add some logging to the webserver, as well as a sentinel file.
  1. Make a 'special' page, ```http://localhost:port/exit.m``` ; when requested, the function ```webserver``` will shut down. This avoids the (obnoxious, IMO) existing solution of calling a script which has a bare ```exit``` in it.
  1. Adding a timeout to ```webserver```, defaulting to ```inf``` for backwards compatibility.
  1. Change file encodings from dos to unix, and add proper endlines.
  1. Attempt to cleanup when Python object dies.

Still to be done:
  1. Better option passing from Python.
  1. Session persistence in ```webserver.```
  1. Better awareness of 'headless' mode in ```webserver``` (_e.g._ a call to ```keyboard``` will likely cause the webserver to hang; similarly, the common idiom of ```dbstop if error```, which exists in my ```startup``` will turn an error in a called function to hang the webserver. These all have to be worked around.)