Rewrite of tiff file reader.
Clarified codepaths based on tiff format to simplify future work of
implementation of seperate contif format.

This commit also includes a few crushed bugs and fixes #9821
(cherry picked from commit 047bd07b7300b7c34e09dce305e311fc1e7dc84e)
more protection against OOM in masks
(cherry picked from commit 088c744ffe312fc915118e468627a154ae136aad)
make it possible to force-disable OpenEXR from the command line

inspired by PR 377 by LebedevRI
(cherry picked from commit 2f051001c3928e8fbdd6ce77c19abb6ecee4a04e)
allow to force-disable webp from the command line

inspired by PR 377 by LebdevRI
(cherry picked from commit 265f55bdbcbaeb6db4c5a48afb460c0f0ff0256c)
Add keywords, as recommended here:

 http://standards.freedesktop.org/desktop-entry-spec/latest/ar01s05.html,
 http://bugs.debian.org/693918, and
 https://wiki.gnome.org/Initiatives/GnomeGoals/DesktopFileKeywords
(cherry picked from commit 9f8bfc4c1bab92d154d228e616befc89bb233261)
Keywords value MUST end with a semicolon
(cherry picked from commit 454f1cf633f06a0ac69212917d4da48c5d281b7f)
.desktop: initial dutch keywords
(cherry picked from commit a1d4baafdc86c08a9ff25bc79b69b14467faeb91)
imageio: lower default jpeg quality to 95

because 7c520cb3dcaba2be619e393c73c22f30f819c90e alone
didn't quite do the job :)
(cherry picked from commit 7657782ca51efaf166f1ba066071627eb319084c)