Edited Build.scala

Added lift-json dependency to deps list
DayOff & ProjectHistoryEntry fixed

Made proper definition for DayOffType and ProjectHistoryEntry.
For example: val dayOffType: DayOffType.Value instead of val dayOffType:
DayOffType
Added new package Service

Basic server with get and post requests.
Had to create case class Employee instead of original Employee for JSON
deserialization to work.
Added service invocation to Main