fix check_in
Merge branch 'bowen' into rtong
Finish CheckInSelectedCourse and CheckAllSimpleAnd Complex interfaces
Merge branch 'rtong' into shuaiwang

Conflicts:
	app/controllers/StudyPlanController.java
	app/controllers/algorithm/req_and_course/TestLinkList.java
asd
add step1 function
Merge branch 'Bohan-Zheng' into rtong
Merge branch 'shuaiwang' into rtong
好了
Merge branch 'Bohan-Zheng' into rtong
delete dead data
Merge remote-tracking branch 'origin/rtong' into bowen