MagFieldElements : move large inline function to .icc, format, tidy
Now that we have the 1st version of the condition data in: took the opportunity
- Follow this from the ATLAS style
it is usually better to split them out into a separate file, with extension ``.icc'', that is included at the end of the header.
- Also do a a bit of code formatting
- Run a few clang-tidy checks on the code.
Mentioning @schaffer
Edited by Christos Anastopoulos