* new difficult mode suggestions (more within the theme of 'knowledge')
* cleaning up new difficulty descriptions, also changing character select titles to match the STORY.txt
* better transparency mask on Easy
* ran optimize-all-img.sh script
* consistency
* (hopefully) got rid of some half-transparent pixels, especially on Normal.webp
* playermode descriptions! (for real this time)
* Reimu shot description changes (as per PR)
* modify ReimuB description
also moved the generated version.c to the build dir to avoid polluting
the source tree and to prevent different build dirs from conflicting
with each other
