add: service tier (ServiceService) for ServiceDao implemented

add: complete tests (ServiceServiceTest) for ServiceService tier
add: spring-tx maven dependency
fix: typo in query in CustomerDaoImpl
fix: test failure due to typo in class and filenam (was EpmloyeeServiceTest instead of EmployeeServiceTest)
extended ServiceDaoImpl with (add|del|update)Service methods
now throwing DataAccessException when a DB error occurs in ServiceDaoImpl
now checking for null in ServiceDto
Merge branch 'master' of https://github.com/martinsakac/pa165