(manual) ID for the code, emit ID + Code
Update programmer.html
changed event "new visitor" for "code update"
Multiple Canvas with unique IDs

The programmer can be manually set to send the code to a specific
canvas ID.
The renderer either create the canvas or if a canvas with this ID
exist, replace the canvas. Then a new processing instance is created
[do processing kill the old instances that used the same canvas ??].
Also, renderer javascript moved to paysagerender.js
Merge pull request #2 from juliendorra/master

Sending a (manual) ID for the code.