Add the concept of a FeedItem that is "in progress"

A FeedItem should be considered "in progress" when the user started
listening or watching the media, but did not complete it yet.

src/de/danoeh/antennapod/feed/Feed.java

@@ -82,6 +82,21 @@ public class Feed extends FeedFile {
 		return count;
 	}
 
+	/**
+	 * Returns the number of FeedItems where the media started to play but
+	 * wasn't finished yet.
+	 * */
+	public int getNumOfStartedItems() {
+		int count = 0;
+
+		for (FeedItem item : items) {
+			if (item.isInProgress()) {
+				count++;
+			}
+		}
+		return count;
+	}
+
 	/**
 	 * Returns true if at least one item in the itemlist is unread.If the
 	 * 'display only episodes' - preference is set to true, this method will

src/de/danoeh/antennapod/feed/FeedItem.java

@@ -128,6 +128,10 @@ public class FeedItem extends FeedComponent {
 		return read;
 	}
 
+	public boolean isInProgress() {
+		return (media != null && media.isInProgress());
+	}
+
 	public String getContentEncoded() {
 		return contentEncoded;
 	}

src/de/danoeh/antennapod/feed/FeedMedia.java

@@ -118,4 +118,8 @@ public class FeedMedia extends FeedFile {
 		this.playbackCompletionDate = playbackCompletionDate;
 	}
 
+	public boolean isInProgress() {
+		return (this.position > 0 && this.playbackCompletionDate == null);
+	}
+
 }