Fix NPE's
Moves differentiated capacity checks from service to domain, removes 'tstyle4' from views
Merge branch 'teacherStudentGroups' into develop

Conflicts:
	src/main/java/net/sourceforge/fenixedu/presentationTier/Action/teacher/StudentGroupManagementDA.java
	src/main/webapp/teacher/executionCourse/executionCourseFrame.jsp