registration page feature

This is a combination of 7 commits:
 - registration feature, model, migration
 - add registration flag to tny and let pawn toggle it
 - follow tournament register link for a new registration, when tny flag on
 - stuff is broken, need to debug at home. rebase this away
 - registration management and page leverages sections
 - registration and registration validation
 - refactored to rename desired_section to section