AmpGen: Apply clang-format

Whitespace only change (with reordering of includes, though) by applying a copy of the official .clang-format file. No functional changes.

Remember to run git ls-files '*.cpp' '*.h' | xargs clang-format -style=file -i before committing (or add it to your git hooks).

Use git blame -w -M when running git blame to ignore whitespace and moving code changes (Don't blame me for everything, in other words!)