Restructure project and redo codes

[keanutaufan]

This codebase is currently messy and there are lots of potential bugs in some of the DS implementations dealing with memory management. Not only that, there is currently no standard for how the code is structured and written. This issue aims to tidy up the codebase, redo problematic codes, and refactor all implementations to meet the style guide and other standards.

This is what I have in mind as for now:

• Refactor code to meet the style guide (once it has been defined)
• Ensure every data structure implementations follow RAII principle and rules of 0/3/5
• Separate source code, tests, and wiki/docs folder
• Encourage Doxygen usage

Since explanations are harder to rewrite, old implementations and its following docs will be kept until new explanations for the rewritten codes have been made. Until then, old files are stored under any folder with legacy_ prefix.