Support access control

[xleclercq]

Suggested format:

{
"title": "Test Site 1",
"homepage": { "page": "pages/index.html" }, // TODO: has to refer to existing content defined below
"navigation": [
{
"label": "Home",
"target": { "page": "pages/index.html" }
}
],
"content": [
"group": // TODO: use of groups should be example 2
{
"access": "public", // TODO: we don't support access control in Nemu yet but pre-empt
"robots": "allow", // TODO: again just an idea for now
"template-engine": "mustache", // TODO: the default template engine, again just an idea for now as we'll assume everything is Mustache by default
// TODO: caching policy
// TODO: a way to explicitly remove a prefix from the URL path that is generated
"content": [
"page": { "path": "pages/index.html" }, // TODO: by default the "id" is the path, we really want to map "pages/whatever" to "https://domain/whatever", how do we achieve this?
"image": { "path": "images/logo.png" },
]
}
"group": // TODO: another group
],
"sitemap": true
}