Fix spelling, spacing, and unused variables (#236)

* Fix spelling, spacing, and unused variables

* Fixed typo in 3 more models

* Added open back

* Remove setBackendAndTarget functions from C++ demos, which are unused functionality.

demo.cpp

@@ -224,7 +224,7 @@ int main(int argc, char** argv)
     else
         cap.open(0);
     if (!cap.isOpened())
-        CV_Error(Error::StsError, "Cannot opend video or file");
+        CV_Error(Error::StsError, "Cannot open video or file");
     Mat originalImage;
     static const std::string kWinName = modelPath;
     while (waitKey(1) < 0)

demo.py

@@ -106,7 +106,7 @@ if __name__ == '__main__':
 
         # Save results if save is true
         if args.save:
-            print('Resutls saved to result.jpg\n')
+            print('Results saved to result.jpg\n')
             cv.imwrite('result.jpg', original_image)
 
         # Visualize results in a new window