Add SGD and MBGD implementations

[Benardi]

Add alternatives to Batch Gradient Descent

Description

Rename gradient_descent to BGD (Batch Gradient Descent). Add SGD (Stochastic Gradient Descent) and MBGD (Mini-Batch Gradient Descent) implementations, test and documentation.

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

How Has This Been Tested?

• [x] Test cases for SGD at Utils Test Suite
• [x] Test cases for MBGD at Utils Test Suite

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules