Fix output stream in textarea. Add blocking actions.

src/main/org/insa/graphics/RunningAction.java

@@ -0,0 +1,33 @@
+package org.insa.graphics;
+
+import java.time.Duration;
+import java.time.Instant;
+
+public interface RunningAction {
+
+    /**
+     * @return true if this action is running.
+     */
+    public boolean isRunning();
+
+    /**
+     * Interrupt this action.
+     */
+    public void interrupt();
+
+    /**
+     * @return Starting time of this action.
+     */
+    public Instant getStartingTime();
+
+    /**
+     * @return Current duration of this action.
+     */
+    public Duration getDuration();
+
+    /**
+     * @return Information for this action.
+     */
+    public String getInformation();
+
+}