Now all buttons have a css-class specifying its function

It is now possible to hide edit- and collapse-buttons like this:

    <style>

        .json-editor-btn-edit
        {
            display: none;
        }

        .json-editor-btn-collapse
        {
            display: none;
        }
    </style>
Merge pull request #87 from mbknor/specific-button-classes

Now all buttons have a css-class specifying its function