New tileSourceType 4 for tilelayer.js
New tileSourceType 4 for tilelayer.js

Defined as: <URL>/zoom/X_Y.<extension>

Aims at reducing the number of tiles per section folder
by dividing by the number of zoom levels, which should
result in increased file lookup performance.

fzadow/CATMAID,htem/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID