Mutation tests UI

I've developed UI for mutation test infrastructure in order to simplify the process of running mutation tests.
Special menu items in DynamoView were created:
- Select tests - an ability to select tests to be run. List items are binded to CompositeCollection in MutatorDriver, where we dynamically build this collection from the available mutation tests marked with MutationTest attribute.
- Run here - run selected tests on the current document (RunMutationTests)
- Run on selected folder - an ability to run selected tests on saved files from the selected folder (RunOnSelectedFolder() function from MutatorDriver class).

 


Long statement, the following would have been more readable:

```cs
var attribs = Attribute.GetCustomAttribute(type, typeof(MutationTestAttribute));
var attribute = attribs as MutationTestAttribute;
if (attribute != null)
{
}
```