fix conflict in course
Merge branch 'rtong' into Bohan-Zheng
Merge branch 'Bohan-Zheng' of https://github.com/xixixhalu/sss into Bohan-Zheng
Merge branch 'rtong' into Bohan-Zheng
123
?
??
cv
yeah
j
Merge branch 'shuaiwang' into Bohan-Zheng

Conflicts:
	.gitignore
	.target/views/course_add.scala.html
	.target/views/course_edit.scala.html
	.target/views/course_list.scala.html
	conf/application.conf
Merge branch 'rtong' into Bohan-Zheng
1121313
123
bb
algorithm pre_and_core
sb
Merge branch 'shuaiwang' into rtong

Conflicts:
	app/controllers/StudyPlanController.java
	app/controllers/algorithm/pre_and_core/Course_Selection.java
	conf/application.conf
Merge branch 'rtong' into shuaiwang
fix bug: if a simple requirement already exists