Filter and Exception namespace

- Filter class cleaned upevery class inside that file got moved to his own file.
- FilterException got moved to the namespace Sifo\Exception.
- Using Filter namespace in the classes that need it.
- Moved every exception under Sifo/src to a new namespace under Sifo\Exception
- "use" namespaces where needed
- Changes to exception names where usages were found under Sifo/src