added yolo4x and yolo4-csp from the github repo and download file corrections

tests/darknet/cfg/yolo4x.cfg

@@ -5,8 +5,8 @@
 # Training
 batch=64
 subdivisions=8
-width=672
-height=672
+width=640
+height=640
 channels=3
 momentum=0.949
 decay=0.0005
@@ -15,7 +15,7 @@ saturation = 1.5
 exposure = 1.5
 hue=.1
 
-learning_rate=0.00261
+learning_rate=0.001
 burn_in=1000
 max_batches = 500500
 policy=steps
@@ -26,6 +26,8 @@ mosaic=1
 
 letter_box=1
 
+#optimized_memory=1
+
 [convolutional]
 batch_normalize=1
 filters=32
@@ -1131,6 +1133,7 @@ size=1
 stride=1
 pad=1
 activation=mish
+stopbackward=800
 
 ##########################
 
@@ -1147,7 +1150,7 @@ size=1
 stride=1
 pad=1
 filters=255
-activation=linear
+activation=logistic
 
 
 [yolo]
@@ -1156,6 +1159,7 @@ anchors = 12, 16, 19, 36, 40, 28, 36, 75, 76, 55, 72, 146, 142, 110, 192, 243, 4
 classes=80
 num=9
 jitter=.1
+scale_x_y = 2.0
 objectness_smooth=0
 ignore_thresh = .7
 truth_thresh = 1
@@ -1169,6 +1173,7 @@ iou_loss=ciou
 nms_kind=diounms
 beta_nms=0.6
 new_coords=1
+max_delta=5
 
 [route]
 layers = -4
@@ -1275,7 +1280,7 @@ size=1
 stride=1
 pad=1
 filters=255
-activation=linear
+activation=logistic
 
 
 [yolo]
@@ -1284,6 +1289,7 @@ anchors = 12, 16, 19, 36, 40, 28, 36, 75, 76, 55, 72, 146, 142, 110, 192, 243, 4
 classes=80
 num=9
 jitter=.1
+scale_x_y = 2.0
 objectness_smooth=1
 ignore_thresh = .7
 truth_thresh = 1
@@ -1297,6 +1303,7 @@ iou_loss=ciou
 nms_kind=diounms
 beta_nms=0.6
 new_coords=1
+max_delta=5
 
 [route]
 layers = -4
@@ -1403,7 +1410,7 @@ size=1
 stride=1
 pad=1
 filters=255
-activation=linear
+activation=logistic
 
 
 [yolo]
@@ -1412,6 +1419,7 @@ anchors = 12, 16, 19, 36, 40, 28, 36, 75, 76, 55, 72, 146, 142, 110, 192, 243, 4
 classes=80
 num=9
 jitter=.1
+scale_x_y = 2.0
 objectness_smooth=1
 ignore_thresh = .7
 truth_thresh = 1
@@ -1425,3 +1433,4 @@ iou_loss=ciou
 nms_kind=diounms
 beta_nms=0.6
 new_coords=1
+max_delta=2