refactoring, combine assessment column preference related model method to one method
refactoring: reduce the number of named scope in course preferences by using joins and extensions in scope
refactoring: use joins and extensions to provide common interface for access course preference items
refactoring, leave only one page preference method in course model
exclude tagging from mission edit page
combine mission and training index to one under assessment.index
update models to allow update and access
create general question controller under assessment
temporarily comment out pending action in home page
update course ability due to schema change
remove unused scope in course preference
update tag model to allow use get all assessments with questions tagged by selected tags
combine mission and training index template into one
update routes, submission directly under assessment module
replace seen training and seen mission with seen assessment
add is_correct for std mcq all answer
add class name for question  in question assessment relationship model
skip verify_authenticity_token
fix unseen notification count for mission and training
fix mission action for students