Linter and code style

[moggers87]

• Add cppcheck and fix errors it raises
• Add clang-format
• Add various warnings that aren't enabled by default and done a general clean up
  • Changed some switch statements into ifs
  • Given switch statements a default case
  • Removed functions that now appear in std
  • Added blocks to prevent shadowing
• Added editorconfig
• Run checks on CI

Fixes #19