Feature: add session data consumption information in GUI/text UIs (#287)

* Feature: add session data consumption information in GUI/text UIs

Adds the total bytes downloaded and uploaded in the current session as well as the average data transfer rate for both UL/DL. The information is not added to the 1-line UI as the line will take 150+ characters in the screen.

src/com/sheepit/client/TransferStats.java

@@ -0,0 +1,36 @@
+package com.sheepit.client;
+
+import lombok.AllArgsConstructor;
+
+/****************
+ * Holds the session traffic statistics. The constructor accepts two parameters:
+ * @long bytes - bytes transferred in the session
+ * @Job seconds - seconds spent transferring the data
+ */
+@AllArgsConstructor
+public class TransferStats {
+	private long bytes;
+	private long millis;
+	
+	public TransferStats() {
+		this.bytes = 0;
+		this.millis = 0;
+	}
+	
+	public void calc(long bytes, long millis) {
+		this.bytes += bytes;
+		this.millis += millis;
+	}
+	
+	public String getSessionTraffic() {
+		return Utils.formatDataConsumption(this.bytes);
+	}
+	
+	public String getAverageSessionSpeed() {
+		try {
+			return Utils.formatDataConsumption((long) (this.bytes / (this.millis / 1000f)));
+		} catch (ArithmeticException e) {	// Unlikely, but potential division by zero fallback if first transfer is done in zero millis
+			return Utils.formatDataConsumption((long) (this.bytes / (0.1f)));
+		}
+	}
+}