add icons to sidebar

[macrozone]

You are now able to add icons to the sidebar.

• [x] impl. for bootstrap
• [ ] impl. for material
• [ ] add documentation

You can add icons through orion.links, e.g.

orion.links.add({
    identifier: "test",
    title: "Test page",
    iconClass: "fa fa-bluetooth",
    index: 100
});

Or on collections:

SchoolClasses = new orion.collection("SchoolClasses", {
    singularName: "Class",
    pluralName: "Classes",
    link: {
        iconClass: "fa fa-graduation-cap",
    },
        ....
});

And so on.

I also added some default icons. Let me know what you think!

[macrozone]

maybe someone can help with materialize-version :+1: