Replaced direct calls to jobQ, changeTime, totalWait, numTasks, and
activeJob fields in Machine with getJobs(), getChangeTime(),
getTotalWait(), getNumberOfTasks(), getActiveJobs(), setChangeTime(),
setTotalWait(), setNumberOfTasks(), and setActiveJob() methods. Set
jobQ, changeTime, totalWait, numTasks, and activeJob fields to private.
All tests pass.