Full group refactoring + translation
Changes to be committed:
	modified:   school-service/src/main/java/school/service/GroupService.java
	modified:   school-service/src/main/java/school/service/implementation/CourseServiceImpl.java
	modified:   school-service/src/main/java/school/service/implementation/GroupServiceImpl.java
	modified:   school-web/src/main/java/school/controller/GroupController.java
	modified:   school-web/src/main/java/school/controller/GroupEditController.java
	modified:   school-web/src/main/resources/messages_en.properties
	modified:   school-web/src/main/resources/messages_ru.properties
	modified:   school-web/src/main/resources/messages_ua.properties
	modified:   school-web/src/main/webapp/resources/js/group-edit.js
	modified:   school-web/src/main/webapp/views/groups/head-teacher.jsp
	modified:   school-web/src/main/webapp/views/groups/student.jsp
	modified:   school-web/src/main/webapp/views/groups/teacher.jsp
Merge branch 'master' of https://github.com/vsomov/SchoolPortal