Re-implement AI controller using new grid-aligned movement algorithm

[nucleartide]

Changelog

What is the "shippable increment" of this pull request?

• Reimplement AGhostAIController using new grid-aligned movement algorithm
• General code cleanup after starting to use JetBrains' Rider
• Wrote my first unit test in Unreal/C++

Dev Checklist

• First draft. Implement a working first pass at the feature/problem.
• Final draft. Perform a general review of Files changed and revise anything that needs to be cleaned up.

Presentation Checklist

• Make a GIF to display what you made.
• Add discussion points to readme.
• Cut a new build in Unreal, and upload a GitHub release.