Code Cleanup Master Issue

[James-Oswald]

Comment any code cleanup issues here with checkboxes.

• : Redo Tools to be imported with just their module names then access handlers with Tool.handler
• : Replace Linked List with regular JS List
• setTool in index.ts should not be exported. This was likened to creating methods in the main() of a Java class. Figure out some fix!
• Get rid of magic numbers in index.ts regarding enums (~line 250)
• Helper function for currentProofTree in ProofTools

          If we need this exact block of code in every single proof mode tool it should be turned into a helper function.

• Nothing from draw tools should be imported by proof tools, should all be moved to a shared tools utils file or folder with multiple files in the src folder.

Originally posted by @James-Oswald in #287 (comment)

[AnushaTiwari5]

• Get rid of magic numbers in index.ts regarding enums (~line 250)
  in pr #286