Minor edits / corrections

1. mangle_into_fdb takes an array of indices instead of params[:hash]
2. marks_if? always returns a fraction >= 0
New column - feedback:integer

Mangled  within this integer is the feedback breakdown given by
an examiner for a particular response

Migration to convert old style calibrations into this new feedback will follow soon
New-style feedback - using new grading panel - can now be submitted

Some bugs noticed. Fixes will follow