Adding clang-format to cmake

[dhynds]

BEGINRELEASENOTES

• Added clang-format to cmake lists and added extra target. "make format" will now format the code, and will be prepared automatically if clang-format exists.
• Updated tracking strategy and added some improvements in terms of refitting tracks each time a hit is added, and included a maximum chi2 criteria for adding hits

ENDRELEASENOTES

[andresailer]

If you just want the clang format in the PR, please drop the other commits, otherwise change the first PR comment to include other changes.
Also: please don't add the UNDEBUG flag permanently. And maybe use some different DEBUG levels and not just a single one

[dhynds]

Ok, removed the commit for forced debug. Added comments in the release notes.