INFRA: Drop numeric XX- from markdown file names

[effigies]

Closes #1323.

[sappelhoff]

argh, I introduced merge conflicts by merging some PRs (I think). Sorry. +1 on merging this as soon as conflicts are resolved.

A potential re-ordering of sections can then follow in another PR that won't be as prone to conflicts.

[sappelhoff]

• note that although the CI "checkmark" for your last commit 3427934 is green, there were failures that I tried to fix with the following commits
• however, the build_docs_pdf check is stubborn, and I can't see what's wrong: locally the PDF builds well ... when logged into circleci via ssh, the problem is the same (perhaps obviously)

[sappelhoff]

Ah, I see one consequence of dropping the XX prefixes now. The PDF build gets screwed up in its order:

bids-specification/pdf_build_src/pandoc_script.py

Lines 23 to 32 in 341a944

	# Get all input files
	markdown_list = []
	for root, dirs, files in os.walk("."):
	for file in files:
	fpath = os.path.join(root, file)
	if fpath.endswith(".md") and fpath not in EXCLUDE:
	markdown_list.append(fpath)
	elif fpath.endswith("index.md"):
	# Special role for index.md
	index_page = fpath

bids-specification/pdf_build_src/pandoc_script.py

Lines 59 to 62 in 341a944

	# Add input files to command
	# The filenames in `markdown_list` will ensure correct order when sorted
	cmd += [str(root / index_page)]
	cmd += [str(root / i) for i in ["../../metadata.yml"] + sorted(markdown_list)]

☝️ as can be seen in these snippets, the build was relying on the order being determined via the file names.

but that doesn't explain why the CI fails (while locally, everything works, albeit with the screwed up ordering)

[sappelhoff]

PDF build is broken (see comments above)

[effigies]

Seems this needs more thought.

[sappelhoff]

probably we could parse mkdocs.yml's "Nav":

bids-specification/mkdocs.yml

Line 52 in 6b09a66

nav:

... then we wouldn't need to have the loop that's dependent on file names, and we wouldn't have to maintain a duplicate list of files just for the PDF build

I attempted this in #1343 ... perhaps merging that and pulling it into this branch would fix the build.