FFmpegReader/Writer: Reformat example code

- Reduced crazy-long line lengths by moving trailing comments to
  previous line
- Added more openshot:: prefixing, which causes Doxygen to link to
  the referenced object's documentation. (It doesn't always pick
  up cross-class links, without the prefix.)

Author: ferdnyc

include/FFmpegReader.h

@@ -76,11 +76,11 @@ namespace openshot {
 	 *
 	 * @code
 	 * // Create a reader for a video
-	 * FFmpegReader r("MyAwesomeVideo.webm");
+	 * openshot::FFmpegReader r("MyAwesomeVideo.webm");
 	 * r.Open(); // Open the reader
 	 *
 	 * // Get frame number 1 from the video
-	 * std::shared_ptr<Frame> f = r.GetFrame(1);
+	 * std::shared_ptr<openshot::Frame> f = r.GetFrame(1);
 	 *
 	 * // Now that we have an openshot::Frame object, lets have some fun!
 	 * f->Display(); // Display the frame on the screen

include/FFmpegWriter.h

@@ -75,15 +75,19 @@ namespace openshot {
 	 * @code SIMPLE EXAMPLE
 	 *
 	 * // Create a reader for a video
-	 * FFmpegReader r("MyAwesomeVideo.webm");
-	 * r.Open(); // Open thetarget_ reader
+	 * openshot::FFmpegReader r("MyAwesomeVideo.webm");
+	 * r.Open(); // Open the target reader
 	 *
 	 * // Create a writer (which will create a WebM video)
-	 * FFmpegWriter w("/home/jonathan/NewVideo.webm");
+	 * openshot::FFmpegWriter w("/home/jonathan/NewVideo.webm");
 	 *
 	 * // Set options
-	 * w.SetAudioOptions(true, "libvorbis", 44100, 2, ChannelLayout::LAYOUT_STEREO, 128000); // Sample Rate: 44100, Channels: 2, Bitrate: 128000
-	 * w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000); // FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
+	 *
+	 * // Sample Rate: 44100, Channels: 2, Bitrate: 128000
+	 * w.SetAudioOptions(true, "libvorbis", 44100, 2, openshot::ChannelLayout::LAYOUT_STEREO, 128000);
+	 *
+	 * // FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
+	 * w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000);
 	 *
 	 * // Open the writer
 	 * w.Open();
@@ -102,15 +106,19 @@ namespace openshot {
 	 * @code ADVANCED WRITER EXAMPLE
 	 *
 	 * // Create a reader for a video
-	 * FFmpegReader r("MyAwesomeVideo.webm");
+	 * openshot::FFmpegReader r("MyAwesomeVideo.webm");
 	 * r.Open(); // Open the reader
 	 *
 	 * // Create a writer (which will create a WebM video)
-	 * FFmpegWriter w("/home/jonathan/NewVideo.webm");
+	 * openshot::FFmpegWriter w("/home/jonathan/NewVideo.webm");
 	 *
 	 * // Set options
-	 * w.SetAudioOptions(true, "libvorbis", 44100, 2, ChannelLayout::LAYOUT_STEREO, 128000); // Sample Rate: 44100, Channels: 2, Bitrate: 128000
-	 * w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000); // FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
+	 *
+	 * // Sample Rate: 44100, Channels: 2, Bitrate: 128000
+	 * w.SetAudioOptions(true, "libvorbis", 44100, 2, openshot::ChannelLayout::LAYOUT_STEREO, 128000);
+	 *
+	 * // FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
+	 * w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000);
 	 *
 	 * // Prepare Streams (Optional method that must be called before any SetOption calls)
 	 * w.PrepareStreams();