A lot of work here and there

A lot of work here and there

DB columns userid renamed to authorid or reviewerid to make the value
clear. Improved manual allocation UI. Raw grades are stored as numeric
values from 0.00000 to 100.00000 (instead of the current 0 to 1) to be
more precise. Started to work on the Grading report (it est the overall
report of all grades form submission and grades for assessments).