Fix typos in tutorials within docs/

Fix various typos found within tutorial documentation

doc/tutorials/ios/image_manipulation/image_manipulation.markdown

@@ -22,7 +22,7 @@ Introduction
 In *OpenCV* all the image processing operations are usually carried out on the *Mat* structure. In
 iOS however, to render an image on screen it have to be an instance of the *UIImage* class. To
 convert an *OpenCV Mat* to an *UIImage* we use the *Core Graphics* framework available in iOS. Below
-is the code needed to covert back and forth between Mat's and UIImage's.
+is the code needed to convert back and forth between Mat's and UIImage's.
 @code{.m}
 - (cv::Mat)cvMatFromUIImage:(UIImage *)image
 {