Wasm playground

[MathJud]

This updates the following:

• create playground folder
  • with Makefile
  • is new default folder for dns.js development
  • moved sd_inspector into this folder
  • created a play.html playground for testing
• sd_inspector
  • implements the WASM library
  • the DNS-SD demo to automatically shows all keys
  • automatically updates the domains when a new key appears
• new JS classes
  • keys.js contains the keys class and the key class
  • domains.js contains the domains class which holds and manages
• dns.js updates
  • the dns class now contains WASM
  • each dns object can old one or several keys
  • the dns object now takes several addition optional construction arguments
  • the dns object can be configured via a construction argument
• New event communication system
  • the keys & domains classes dispatch several events to allow other classes and especially the UI to react on changes.