[Feature Request] Allow to make an display order of module position in config (#3762)

My proposal for #3761 

* I use `flex` box for create region container
* I have moved `container` definition to `main.css` (for css tunning,
maybe it can be useful)
* I create `order` in module config for define module order display from
position

# Advantage:

We don't have to move module config in another place in array of modules

# Another advantage that i did'nt think:

We can change dynamicaly module order of a container:

- So, in this case, for a module config builder, (I won't mention the
name because otherwise I'll get angry...)
It can be usefull for a config preview (before saving config)
--> just change style css `order` module value for see preview

- Or, change `order` value in dev console for testing

# Disadvantages

I don't see any ;)

js/main.js

@@ -30,6 +30,8 @@ const MM = (function () {
 				dom.className = `module ${dom.className} ${module.data.classes}`;
 			}
 
+			dom.style.order = (typeof module.data.order === "number" && Number.isInteger(module.data.order)) ? module.data.order : 0;
+
 			dom.opacity = 0;
 			wrapper.appendChild(dom);
 
@@ -463,7 +465,8 @@ const MM = (function () {
 				}
 			});
 
-			wrapper.style.display = showWrapper ? "block" : "none";
+			// move container definitions to main CSS
+			wrapper.className = showWrapper ? "container" : "container hidden";
 		});
 	};