Fixes IP Cameras Hanging

 - The IPCameraFrameGrabber was stuck in an infinte loop
waiting for the rest of the image to arrive.
This was fixed by using a DataInputStream instead
 - An unexpected end of the stream would cause a null
pointer exception. Now throws an EOFException. WPIRoboticsProjects#390

Closes WPIRoboticsProjects#390
Closes WPIRoboticsProjects#427
Closes WPIRoboticsProjects#404
Closes WPIRoboticsProjects#387
Closes WPIRoboticsProjects#436

core/src/main/java/edu/wpi/grip/core/sources/IPCameraFrameGrabber.java

@@ -33,8 +33,9 @@
 import javax.imageio.ImageIO;
 import java.awt.image.BufferedImage;
 import java.io.ByteArrayInputStream;
+import java.io.DataInputStream;
+import java.io.EOFException;
 import java.io.IOException;
-import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
@@ -72,7 +73,7 @@ public static void tryLoad() throws Exception {
     private URL url;
 
     private URLConnection connection;
-    private InputStream input;
+    private DataInputStream input;
     private byte[] pixelBuffer = new byte[1024];
     private Map<String, List<String>> headerfields;
     private String boundryKey;
@@ -99,7 +100,7 @@ public void start() throws Exception {
                     }
                 }
             }
-            input = connection.getInputStream();
+            input = new DataInputStream(connection.getInputStream());
         } catch (IOException e) {
             // Make sure we rethrow the IO exception https://github.com/bytedeco/javacv/pull/300
             throw new Exception(e.getMessage(), e);
@@ -169,9 +170,9 @@ byte[] readImage() throws IOException {
             }
         }
         // find embedded jpeg in stream
-        String subheader = sb.toString();
+        final String subheader = sb.toString();
         //log.debug(subheader);
-        int contentLength = -1;
+
         // if (boundryKey == null)
         // {
         // Yay! - server was nice and sent content length
@@ -180,18 +181,17 @@ byte[] readImage() throws IOException {
 
         if (c0 < 0) {
             //log.info("no content length returning null");
-            return null;
+            throw new EOFException("The camera stream ended unexpectedly");
         }
 
         c0 += 16;
-        contentLength = Integer.parseInt(subheader.substring(c0, c1).trim());
+        final int contentLength = Integer.parseInt(subheader.substring(c0, c1).trim());
         //log.debug("Content-Length: " + contentLength);
 
         // adaptive size - careful - don't want a 2G jpeg
         ensureBufferCapacity(contentLength);
 
-        while (input.available() < contentLength) ;
-        input.read(pixelBuffer, 0, contentLength);
+        input.readFully(pixelBuffer, 0, contentLength);
         input.read();// \r
         input.read();// \n
         input.read();// \r