BREAKING CHANGE: MVariable added + MArray.remove_elem() added + MArray.append_elem() changed + MArray label and fetch method added + Generic MArrayElement sub-mobjects fetch method added + MArrayElementComp enum added + Changed array.py to m_array.py + Documentation updated

[drageelr]

Overview: What does this pull request change?

• Added remove element function in MArray
• Added label support in MArrayElement
• Added generic mob fetch function in MArrayElement coupled with MArrayElementComp enum
• Changed array.py to m_array.py because of conflict with native array module
• Added variables documentation in references
• Updated module name of m_array in references
• Label with four different direcitons added.
• Label shifts on append and remove element appropriately.
• Update label text doesn't remove previous label, therefore not added in this commit.
• Method to fetch array label.
• Documentation updated to reflect the changes.

Motivation and Explanation: Why and how do your changes improve the library?

• Can now append/remove elements to/from MArray using custom animations.
• Can now have label with MArray in all four directions that shifts whenever elements are added/removed to/from the MArray.
• Can now create and manipulate variables using MVariable.

Further Information and Comments

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section