Exporer driver test

Testcases for project overview, folder view and file view

Requirements git client: https://github.com/devhub-tud/git-server/pull/26
No need to change now, but cool tool to add to your toolbox when using `Guava`:

```java
List<DiffElement> diffElements = Lists.transform(elements, new Function<WebElement, DiffElement>() {
    @Override
    public DiffElement apply(WebElement input) {
        return DiffElement.build(input);
    }
});
```

Or when using Java 8:

```java
List<DiffElement> diffElements = elements.stream()
    .map(element -> DiffElement.build(element))
    .collect(Collectors.toList());
```