Filtering Scripts

This is the FilterFactory implementation with Unit Tests as I have proposed for #54 

Usage of the FilterFactory class would be:

```csharp
.WithScriptsEmbeddedInAssembly(Assembly.GetExecutingAssembly(),
 FilterFactory.ExcludeScriptNamesInFile("scriptnames.txt"))
```
I agree. I was also debating changing FilterFactory to be named "Filters" so it looks nicer from a Readibility perspective. So what do you think about this:

```cs
.WithScriptsEmbeddedInAssembly(Assembly.GetExecutingAssembly(),
 Filters.OnlyIncludeScriptNamesInFile("scriptnames.txt"))
```
and leave the other one as:

```cs
.WithScriptsEmbeddedInAssembly(Assembly.GetExecutingAssembly(),
 Filters.ExcludeScriptNamesInFile("scriptnames.txt"))
```