Remove include directives (#9674)

[sbesson]

Include directives were introduced when maintaining a single source file for UNIX & Windows server installation.

Now instructions have been split again, it does not make sense anymore and adds confusion.

[ghost]

While I don't see anything wrong in the above changes, what was wrong with the use of include directives here?

[sbesson]

@rleigh-dundee :

• directives were originally used to include OS-specific paragraphs. Since the whole page is now OS-specific, there is no valid justification for including these paragraphs rather than including whole subsections for instance.
• Sphinx does a poor job with include directives compared to LaTeX for instance. Included files need to have a different extensions and are not really tracked at the top-level build.

For these reasons, I would be inclined to get rid of all include directives in the documentation for now until we decide on a valid policy about how and where to use them.

[joshmoore]

@rleigh-dundee, any other objections or suggestions? Would you move each of these sections into a separate section with a toctree?

Assuming Roger accepts this for the moment, the output looks trivially correct and ready to merge.

[ghost]

No objections.