Added available method to stream

bindings/java/src/org/sleuthkit/datamodel/ReadContentInputStream.java

@@ -110,4 +110,12 @@ public int read(byte[] b, int off, int len) throws IOException {
 		}
 
 	}
+	
+	@Override
+	public int available() throws IOException {
+		if (position > length) {
+			return 0;
+		}
+        return (int)(length - position);
+    }
 }