Format all files and add clang-format configuration file

[SamVanheer]

Format all files to use the same layout. Currently code written at different times has a variety of formatting that makes reading code harder and more importantly makes searching for certain patterns of code more difficult, requiring complicated regular expressions to account for additional whitespace.

Use clang-format to configure the formatting settings in a way that ensures consistency between users.

See https://devblogs.microsoft.com/cppblog/clangformat-support-in-visual-studio-2017-15-7-preview-1/ and https://docs.microsoft.com/en-us/visualstudio/ide/reference/options-text-editor-c-cpp-formatting?view=vs-2019 for Visual Studio integration information.

See https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html for ClangFormat 13.0 documentation.

Use this Visual Studio extension to apply formatting rules to all files in a project at once (note: will take some time to apply): https://marketplace.visualstudio.com/items?itemName=munyabe.FormatAllFiles