Add a template based class to each node in the resource tree.

**This pull request has been updated in another pull request:** https://github.com/modxcms/revolution/pull/757

Pattern: class="template_xx" (x is the id of the current template)

By adding a few lines of code to manager/templates/default/css/index.css you can add a custom icon to each resource with a specific template.

Lets say we have 3 templates

Simple Text page (ID:5)
Gallery (ID:6)
Event (ID 7)

**Example css:**
div.template_5 .x-tree-node-icon {
    background-image: url("../images/restyle/icons/text_dropcaps.png")!important;
}
div.template_6 .x-tree-node-icon {
    background-image: url("../images/restyle/icons/picture.png")!important;
}
div.template_7 .x-tree-node-icon {
    background-image: url("../images/restyle/icons/calendar.png")!important;
}

**The screenshot shows the benefits:**
![Template based resource icons](https://dl.dropboxusercontent.com/u/1840535/Download.png)