Added Filter Plugin

This PR adds a new Plugin to make filtering as easy as possible by offering these two features:

1. Generate a Dropdown select with all available values for that property
```html
<div data-filter="dropdown" data-filter-property="consultant"></div>
```

2. Use data-property and data-filter-set to activate filtering:
```html
<ul data-filter-property="evaluation">
	<li>
		<a data-filter-set="">All</a>
	</li>
	<li>
		<a data-filter-set="green">Good</a>
	</li>
	<li>
		<a data-filter-set="red,yellow,orange">Bad</a>
	</li>
</ul>
```

Included is an example page to demonstrate these features as well.

If some code isn't up to your standards/liking, feel free to nag me about it :)