Add support for codemirror schema

[NetDevArt]

[Quick and dirty]
In order to use codemirror autocompletion for xml, we need to define a special json schema :

"!top": ["toplevel"],
toplevel: {
    "children": ["sublevel", "sublevel2"]
},
sublevel: {
    "children": []
},
sublevel2: {
    "children": []
}

An example here : var tags = {...}

So I updated your code by adding a parameter to activate the codemirror format which override the initial built schema.