WIP: clang format
This is a test showing what clang-format does when run on libUtil/*.cpp.
Three different styles are given, I'm not sure what peoples preferences are, but there is also the option of making a custom .clang-format file.
See the docs for details:
https://clang.llvm.org/docs/ClangFormatStyleOptions.html
(note that currently this is using version 11 and 12 is available in LCG on cvmfs)
Also, I removed all the other jobs so the build is quicker for now.