Dao refactor + first services test(MOKITO)
 Changes to be committed:
	modified:   school-dao/src/main/java/school/dao/GroupDao.java
	modified:   school-dao/src/main/java/school/dao/StudentDao.java
	modified:   school-dao/src/main/java/school/dao/TeacherDao.java
	modified:   school-dao/src/main/java/school/dao/implementation/GroupDaoImpl.java
	modified:   school-dao/src/main/java/school/dao/implementation/StudentDaoImpl.java
	modified:   school-dao/src/main/java/school/dao/implementation/TeacherDaoImpl.java
	modified:   school-dao/src/main/java/school/model/Group.java
	modified:   school-dao/src/main/java/school/model/Student.java
	modified:   school-dao/src/main/java/school/model/Teacher.java
	modified:   school-dao/src/test/java/school/dao/implementation/StudentDaoImplTest.java
	modified:   school-dao/src/test/java/school/dao/implementation/TeacherDaoImplTest.java
	modified:   school-service/src/main/java/school/service/implementation/GroupServiceImpl.java
	modified:   school-service/src/test/java/school/service/implementation/CourseServiceImplTest.java
	modified:   school-web/src/main/webapp/views/tiles/sidebar.jsp