[0.4.14][REACTOS] Optimize existing PNGs (#5486) (#5492) (#5506)

This ports back the following commits about lossless PNG-shrinking:
0.4.15-dev-6410-g cf4bb8fced [WALLPAPERS] Optimize PNG images (#5506)
0.4.15-dev-6398-g e5993f13f0 [REACTOS] Optimize PNG images (#5492)
0.4.15-dev-6376-g 8f3a09722e [MSPAINT] Optimize images for help docs (#5486)

Most of those PNGs have not been touched ever since we switched from SVN to git, so they can safely be ported back by copying over.
Only the Mizu-wallpapers had something specific to take care about:
They were added (still with a different name) by 0.4.12-dev-819-g 181a2b3359 [WALLPAPER] Add ReactOS Soft Blue
Later they were renamed by 0.4.14-dev-1435-g 6a8c894642 [WALLPAPER] Rename Soft Blue to Mizu (#1945)
and with that commit a fourth pic was added for Mizu.
Since they are only copied to iso but are not explicitly referenced by the theme, I decided
to port back the renaming part (without adding the fourth pic) to releases/0.4.12 and 0.4.13 to harmonize their name everywhere.
But did not port them back any further than where they existed already.

Tweak a few related txt/md/html files also with trivial stuff like EOL-whitespace-removal.

modules/wallpapers/Silhouette/README.md

@@ -1,7 +1,7 @@
 # Silhouette wallpaper collection
 
 This is a collection of wallpapers lisenced for use
-in the reactOS project. This work is licensed under a 
+in the ReactOS project. This work is licensed under a
 Creative Commons Attribution 4.0 International License.
 
 The original work can be found [here](http://ever3st.com/Graphics/Loot/)