Add Constrained Relevance Matrix to GMLVQ

[Seremath]

Is your feature request related to a problem? Please describe.
A variant on GMLVQ that fixes a single feature relevance. By using fixed relevance one is able to investigate the impact of different relevance values for a single feature. This method is able to lessen the inconsistencies caused by correlations between features.

Describe the solution you'd like
Adding an option to fix the relevance of a single feature during normalization.

Describe alternatives you've considered
N/A

Additional context
N/A