Feature: allow the client to shut down the computer at or after a certain time (#249)

A new -shutdown <time> option has been created to specify the time when the client will stop asking for new jobs, will finish uploading the frames in the upload queue and will shutdown the computer. The time argument can have two different formats: an absolute date & time in the format yyyy-MM-ddThh:mm:ss (24h format) or a relative time in the format +m where m is the number of minutes from now.

The user can also select the shutdown-mode, where "wait" will wait for all the processes (render + pending uploads) to finish and "hard" will cancel all the pending jobs and will initiate the computer shutdown.

src/com/sheepit/client/Configuration.java

@@ -60,6 +60,8 @@ import lombok.Data;
 	private boolean detectGPUs;
 	private boolean printLog;
 	private List<Pair<Calendar, Calendar>> requestTime;
+	private long shutdownTime;
+	private String shutdownMode;
 	private String extras;
 	private boolean autoSignIn;
 	private boolean useSysTray;
@@ -89,6 +91,8 @@ import lombok.Data;
 		this.setCacheDir(cache_dir_);
 		this.printLog = false;
 		this.requestTime = null;
+		this.shutdownTime = -1;
+		this.shutdownMode = "soft";
 		this.extras = "";
 		this.autoSignIn = false;
 		this.useSysTray = true;