Group pages for student/teacher/headteacher were added.
Changes to be committed:
	modified:   ext-resources/db_filling_up.sql
	modified:   school-dao/src/main/java/school/dao/GroupDao.java
	modified:   school-dao/src/main/java/school/dao/implementation/GroupDaoImpl.java
	new file:   school-dao/src/main/java/school/dto/GroupDTO.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/CourseServiceImpl.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/img/logos/2.png
	new file:   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
	modified:   school-web/src/main/webapp/views/tiles/sidebar.jsp