Add `.clang-format` File

[itzmeanjan]

Right now we don't have .clang-format file for dudect, so source formatting is not consistent across IDEs. I propose we adopt "Mozilla" code style template from ClangFormat. See https://clang.llvm.org/docs/ClangFormatStyleOptions.html.

Generate .clang-format config file

clang-format --style=Mozilla --dump-config > .clang-format

And update Makefile (add new Make recipe) so that all source code living inside the repository is consistently formatted.

[itzmeanjan]

@oreparaz I'll send a PR in sometime, just so that we can see the diff.