Remove server console.log calls
Remove IE8 support

It was not supported in other areas anyway
Fix #14.

I introduced a bug by adjusting first the model, then the DOM.

I thought it was more logical, but did not think it had side effects.
When updateLayerDOM checked if the model was different, it had
already been adjusted.

I'll call this the "Unrender bug".
Client now uses modifiedCache when receiving all layers

Now, when a user arrives to a room, and layers are being modified,
the borders correctly indicade those ongoing modifications made
by others.
Better naming of variables, add comments.