Clang-format config

I remember Dave expressed an interest in clang-format a while ago. I added a skeleton clang-format config file to #67. 

There is a nice config-file generator here:
https://zed0.co.uk/clang-format-configurator/
if tweaks are needed.

Is there interest in reformatting the entire codebase? (since there seems to be a lot of refactoring happening at the moment)
