Merge pull request #1 from ctrucza/master

Code review on HolidayRequest
Hard copy of existing project.
Added Email class.\nRemoved dependency from HolidayRequest to EmailServer.
Added Manager class.
Added address property on Employee.
Added manager field to HolidayRequest.
Partially removed dependency from HolidayRequest to Addressbook.
Removed Addressbook class.
Minor refactoring.
Added SubmitForApproval() method.
Informing manager about request via email.
Renamed a method.
Some refactoring.
Added bit of code for storing a request.
Added reference to system.core.
Removed bits of duplication.
Improved a bit the mock object.
Improved a bit the tests.
Bit of formatting.