Cleanup: Spelling Mistakes

This patch fixes many minor spelling mistakes, all in comments or
console output. Mostly contractions like can't, won't, don't, its/it's,
etc.

Differential Revision: https://developer.blender.org/D11663

Reviewed by Harley Acheson

tests/python/batch_import.py

@@ -167,7 +167,7 @@ def main():
     parser.add_option("-S", "--start", dest="start", help="From collected files, start with this index", metavar='int')
     parser.add_option("-E", "--end", dest="end", help="From collected files, end with this index", metavar='int')
 
-    options, _args = parser.parse_args(argv)  # In this example we wont use the args
+    options, _args = parser.parse_args(argv)  # In this example we won't use the args
 
     if not argv:
         parser.print_help()