ENH: apply spelling.patch from DebianGIS

This is a big one without much harm. It fixes incorrect spelling
and grammer when packaging OTB 5.0.0 and 5.2.0 for Debian.
Most of these changes are done by developers at DebianGIS.
For more info, I include the original patch header below.
Description: Fix some spelling errors to silence lintian
enabling  to concentrate on the real problem.
Author: Andreas Tille <tille@debian.org>
Author: Rashad Kanavath <rashad.kanavath@c-s.fr>
Author: Bas Couwenberg <sebastic@xs4all.nl>
Last-Update: 2015-12-22