ol-ext: Fast edge detection filter

SVG filter comes with a set of fast operators to detect edge on map layers.
Filter:

ol/ext/SVGFilter/Laplacian is a simple edge detector filter to detect edges on images.
The Laplacian operator uses a single 3×3 kernel to detect edges.
```
-1 -1 -1
-1  8 -1
-1 -1 -1
```
or
```
 0 -1  0
-1  4 -1
 0 -1  0
```
ol/ext/SVGFilter/Prewitt is a Prewitt like operator.
the operator uses two 3×3 kernels which are convolved with the original image to calculate approximations of the derivatives - one for horizontal changes, and one for vertical.
```
+1  0 -1
+1  0 -1
+1  0 -1
```
&
```
+1 +1 +1
 0  0  0
-1 -1 -1
```
ol/ext/SVGFilter/Roberts is Roberts cross like operator.
the operator the following two kernels.
```
+1  0  0
 0  0  0
 0  0 -1
```
&
```
 0  0 +1
 0  0  0
-1  0  0
```
ol/ext/SVGFilter/Sobel is Sobel like operator.
The operator uses two 3×3 kernels which are convolved with the original image to calculate approximations of the derivatives – one for horizontal changes, and one for vertical
```
+1  0 -1
+2  0 -2
+1  0 -1
```
&
```
+1 +2 +1
 0  0  0
-1 -2 -1
```

@See: SVG filter comparison