As color, hatching and gradient palettes are now handled by
extensions, this patch include:
- Refactor of xhp tags
- move palette_file from simpress/ to shared/
- adjust tree files
- add entry to shared/guide tree
Change-Id: Ied501dd86431d26d09ed91249c22f422620b16d6
Reviewed-on: https://gerrit.libreoffice.org/c/help/+/135096
Tested-by: Jenkins
Reviewed-by: Olivier Hallot <olivier.hallot@libreoffice.org>