cluster_context: Create the cluster context
In unmnn/CluReAL: Clustering Refinement ALgorithm

Create the cluster context

1	cluster_context(x, y)

`x`	The input data (numeric matrix).
`y`	Cluster membership indices (integer vector). -1 indicates noise.

A list with the following elements:

k: The number of clusters (integer).
centroids: Centroid coordinates (k x n matrix).
mass: Cluster sizes (integer vector of length k).
mn_da: Mean Euclidean distances of the cluster members to their centroid (double vector of length k).
md_da: Median Euclidean distances of the cluster members to their centroid (double vector of length k).
sd_da: Standard deviation of the Euclidean distances of the cluster members to their centroid (double vector of length k).
de: Euclidean distance matrix for the centroids (k x k matrix).
outliers: The number of outliers (integer).