Don't allow block generation unless system clock is accurate.

Controller performs NTP check on startup (and every 5 minutes)
which determines whether block generation is allowed.

System Tray tooltip updated to reflect generating status.
Plus new translations.

Improved GuiTests.

BlockGenerator fetches forging accounts first, and sleeps
if none configured, which is less work than processing peer lists.

src/test/java/org/qora/test/GuiTests.java

@@ -19,9 +19,7 @@ public class GuiTests {
 	public void testSysTray() throws InterruptedException {
 		SysTray.getInstance();
 
-		while(true) {
-			Thread.sleep(2000L);
-		}
+		Thread.sleep(10_000L);
 	}
 
 }