Add different image formats

[yuripourre]

Java side:

class FakeCam {
  public static final int V4L2_PIX_FMT_YUV420 = 1;
  public static final int V4L2_PIX_FMT_RGB24 = 2;
}

C side:

#define FMT_YUV420 1
#define FMT_RGB24 2

JNIEXPORT jint JNICALL Java_com_harium_hci_fakecam_FakeCam_open(JNIEnv* env, jobject obj, jstring device, jint width, jint height, jint format) {
  switch(format) {
    case V4L2_PIX_FMT_YUV420:
      format = V4L2_PIX_FMT_YUV420;
    break;
    ....
  }
  initWithFormat(..., format);
}