This patch includes the some structural changes for the sculpt_paint manual.
A lot of duplicated and scattered information is avoided this way.
It will also be the base for rewriting various sections to update outdated pages and make the manual more accessible.
Here's a list of the various changes in this patch.

Sculpting & Painting:

• Moved information about "Selection Masking" and visibility control out of "Brush", and instead into their own page called "Selection & Visibility"
• Various wording updates to make the selection masking page more accurate
• Small updates to the Introduction to make the information more accurate

Brush Settings:

• Merged all "Brush Settings" pages of the painting and sculpting modes into one page. All the mode specific pages now link to the root page.
• Removed the "Texture Mask" page and instead added necessary information to the "Texture" page. This avoids a lot of duplication.

Sculpting:

• Added brief introductions about all the major features of sculpt mode. Various high level information from "Tool Settings", "Tools" and "Editing" was moved here, as well as a lot of new information, to give a birds eye overview and avoid scattering vital information.
• Introduction.rst was split into various introduction pages for easier reading
• The introduction page is more heavily linking to other UI references for specific information
• Removed the "Adaptive" page, since its information has moved to the introduction.
• Categorized the toolbar page for an easier overview of related features and the logic behind the order
• Moved Topology Rake documentation from Dyntopo page to Brush Settings
• Added and updated various visual examples
• Various other small changes to outdated information and shortcuts