Now headteacher can add or remove groups
Changes to be committed:
	new file:   school-dao/src/main/java/school/dto/GroupDataDTO.java
	new file:   school-dao/src/main/java/school/dto/TeacherDTO.java
	modified:   school-dao/src/main/java/school/model/Group.java
	modified:   school-service/src/main/java/school/service/GroupService.java
	modified:   school-service/src/main/java/school/service/implementation/GroupServiceImpl.java
	modified:   school-web/src/main/java/school/controller/GroupController.java
	new file:   school-web/src/main/webapp/resources/css/group.css
	new file:   school-web/src/main/webapp/resources/js/group.js
	modified:   school-web/src/main/webapp/views/groups/head-teacher.jsp