Initial commit for the K-Means Clustering
Updated:
	- Documentation: now everything is in spanish
	- The basic steps (methods) have been added to the
KMeansClustering.java in order to code it later easily.
Added:
	- A custom exception for managing the options for the initialization of
the K-means Clustering algorithm.
Preparing the merge
Initialization finished.
Started the K-means++ initialization algorithm.

Documentation updated.
Substituted the type of the centroids, now they are Instances
Changed the style of the documentation.

The static classes no longer exist, now, every class is instantiable.
This change is required for the K-Means clustering.

Deleted the knntest file.
Centroid class added which is a specialization of Instance. It supports
the modification of it's attributes. Modified the code to support this
new class.

In Instance class changed the attributes modifier from private to
protected. This way, the Centroid class can directly change it's parents
attribute.