Ability to build individual sections with refs, appendices

[joncamfield]

Moved in from SAFETAG/SAFETAG#82

It should be possible to build a specific SAFETAG guide section that pulls in the relevant endnotes and appendices (e.g. example/ content) for that section.

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This is very possible. Currently the makefile just targets the main index's. We would want to actually script up the current builder to be more than a makefile. Once we do this it could do much much more. Here is what it would look like in make speak, but we would want to actually transition it into a language that is robust.

INDEX=path/to/index/file.md
INDEX_NAME=file_name
create_your_own: | $(SRC_DIR) $(DOC_DIR)
    modules/markdown-pp/markdown-pp.py $(INDEX) $(SRC_DIR)/$(INDEX_NAME).md
    pandoc -s --variable=title:"$(INDEX_NAME)" \
        --template=theme/html5.template \
        --to=html5 $(SRC_DIR)/$(INDEX_NAME).md \
        --output=$(SRC_DIR)/$(INDEX_NAME).html 
    wkhtmltopdf --user-style-sheet theme/core.css \
        --title "$(INDEX_NAME)" \
        --disable-smart-shrinking  \
        --load-error-handling skip \
        --load-media-error-handling skip \
        --footer-center "Page [page] of [toPage]" \
        --header-left [doctitle] \
        --outline \
        --outline-depth 2 \
        $(SRC_DIR)/$(INDEX_NAME).html $(DOC_DIR)/$(INDEX_NAME).pdf || true

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Note that this is very close, but due to the SAFETAG per-chapter indices being at a different directory level than the master indices, the copy to tmp/.../target must stay at the root of the content, but the ../ structure in the index/ files can't correctly reference out.

This might end up being a SAFETAG issue again, or an extra doc builder option for the "working" directory?