UI: Fix Typos in Comments and Docs

Approximately 91 spelling corrections, almost all in comments.

Differential Revision: https://developer.blender.org/D10288

Reviewed by Harley Acheson

source/blender/render/intern/pipeline.c

@@ -1971,7 +1971,7 @@ void RE_RenderFrame(Render *re,
     if (write_still && !G.is_break) {
       if (BKE_imtype_is_movie(rd.im_format.imtype)) {
         /* operator checks this but in case its called from elsewhere */
-        printf("Error: cant write single images with a movie format!\n");
+        printf("Error: can't write single images with a movie format!\n");
       }
       else {
         char name[FILE_MAX];