PreviouslyOPAT files were indexed using X and Z now they are indexed with a general index vector.
BREAKING CHANGE: all methods wch used X and Z now use std::vector<double> index (size: header.numIndex) instead. Also added a method to validate tables using checksum
opatIO can now read tables properly and retreive them in a useful manner. Future aditions will be the ability to lookup "closest" tables and a pretty printer for tables.