Allow array in stylesheets declarations in templates.json

[fdelaneau]

Instead of:

"help": {
    "stylesheets": [
        {
            "url": "/css/page.css"
        },
        {
            "url": "/css/factsheet.css"
        },
        {
            "url":  "/css/help.css"
        }
    ]
},

Allow the same format as for javascripts declarations:

"help": {    
    "stylesheets": [ 
        "/css/page.css",
        "/css/factsheet.css",
        "/css/help.css"
    ]
}

If possible allow a mix and match:

"help": {    
    "stylesheets": [ 
        {
            "media": "screen",
            "url":"/css/page.css"
        },
        "/css/factsheet.css",
        "/css/help.css"
    ]
}