tauRecTools: improve the coding style

Improve the coding style of several tools by

• use range-based for when possible
• remove unused functions
• simplify the codes by adding a few functions
• add doxygen style comments

There are a few remaining issues, including

• cell weights are not applied consistently
• vertex correction is not applied correctly to custom pi0 cluster
• some cells could have more than one neighbor in the eta direction, which is assumed to be one These will be addressed in a follow-up MR.