weighted grade functionality

- weights allowed: 1 to 10
- fixed some file extensions for hackerearth language support
- fixed db related bugs: floats instead of ints for grade
auto_judge now grades according to max_grade
assignments scenarios: weight validation

- weights sum up to max grade (3 digit precision)
remove unnecessary echo
just some comments
Merge branch 'weighted-grade1' of https://github.com/divined2004/openeclass into divined2004-weighted-grade1

Conflicts:
	modules/work/index.php
Merge branch 'divined2004-weighted-grade1'