added test project.
created job class.
add name property.
implement job.start
implement job.stop.
changed order only.
Changed names of tests.
Added application image.
added JobManager Class.
deleted
JobManager added.
implementing JobManager.cs.
implemented isRunning field.
refactored test codes.
initialize endTime when it created.
initialized startTIme when job is created.
added Assert.
when job starts, set endTime to DateTime(0).
implemented currentWorkingTime method.
currentWorkingTime returns TimeSpan(0) when job is finished.
implemented totalWorkingTime field.