Merge pull request #1 from hiepluonghlv/separate/hlv/current_dev

Separate/hlv/current dev
Merge pull request #2 from hiepluonghlv/separate/hlv/current_dev

Separate/hlv/current dev
Fixed array as nil error within question banks view
Merge branch 'cur/wy/dev' of https://github.com/Weiyuan-Lane/coursemology.org.git into cur/wy/dev
Added new tables to encompass policy mission functions
Reedited existing table model submission to relations with progression group
Resolve display bugs for new policy mission page
Modify models for policy mission

Signed-off-by: weiyuan_lane <weiyuan.lane@gmail.com>
Resolve bugs for adding new policy mission - questions

Signed-off-by: weiyuan_lane <weiyuan.lane@gmail.com>
Resolve PolicyMissionController invoking Mission model instance
Resolve bug elsif (from else if) in assessment view
Added option for policy mission within student's menu
Added policy mission functionality excluding the grading show component
Added a consecutive option to be expanded on in the future for policy mission
Added consecutive question answering for policy mission
Added statistics screen for students
Added admin statistics interface and excel download
Reformatted excel download for policy mission statistics
Rectified display issue for policy missions to come under training.
Pre stable version before merge with Hiep's code.
Note that there is still some redirect issues with policy missions under training menu
Revised table view for policy missions to be a tab view under trainings
Merge branch 'cur/wy/dev' of https://github.com/Weiyuan-Lane/coursemology.org into Weiyuan-Lane-cur/wy/dev

Conflicts:
	app/models/assessment/grading.rb
	app/views/layouts/application.html.erb
	db/schema.rb