New methods for addDestination and addDestinationsDefinedByHostsOnFacility

- method addDestination for list of Services
- method addDestinationsDefinedByHostsOnFacility for listOfServices
- method addDestinationsDefinedByHostsOnFacility for only already assigned services on facility
- helping private method addDestinationEvenIfAlreadyExists which do not throw exception if destination already exists, only return this destination.
- basic tests for all three methods
Merge pull request #102 from stavamichal/addDestinations-newMethods

New methods for addDestination and addDestinationsDefinedByHostsOnFacility