Two new classes for data types. The MediaFile.java class is a generic
class for audio and video files. The VideoMediaFile.java class is an
especif java class to deal with video files.

The VideoMediaFile.java class has its own private variables, for video
and audio streams, for example.

Another test method has been developed in DocumentClustering.java to
test the new data types classes and the future extract and similarity
classes for these data types.