New project: echoplexus #100

* logo from https://github.com/qq99/echoplexus/blob/master/assets/echoplexus-logo.png resized to 130×130 and centered in 160×160
* license from https://github.com/qq99/echoplexus/blob/master/LICENSE
* introduction from https://github.com/qq99/echoplexus/blob/master/README.md (excerpt)

Echoplex is too good to wait for someone to do this in some months (even not sure), so here’s it! 
@jancborchardt Hmmm, I admit "chat" isn’t everything about echoplexus, but if you write “collaboration”, one would perhaps imagine something like Google Docs, where you can share all the materials of a project (or like github for coding!). With echoplexus, you can draw something and share some code snippets, but you still need some other means for working on any project. Maybe “group communication”?