In https://github.com/OpenTechStrategies/ots-doctools/pull/10,
@choeppler points out (#pullrequestreview-425924575) that the "OTSDIR"
environment variable should not be required to be set, since only
"OTS_DOCTOOLS_DIR" is documented, and that furthermore if we are going
to check paths under "OTSDIR" we should at least do it in the same
order relative to "OTS_DOCTOOLS_DIR" that 'Makefile.docspecific' uses.

This commit is his suggested patch from that PR review.  (Note that
the commits in that PR are actually already applied.  There must have
been a rebasing somewhere along the way, as they all have different
commit IDs in master than they do in the PR.)

  * Detect inkscape version of 1.0 rc 1 or later and add some tex to
    call inkscape using new-style command line parameters.

  * Add a preambles loop to the base jinja template so we have an easy
    way to add preamble sections that doesn't require clobbering the
    existing preamble items

  * Add a dump function to pipeline.py so we can dump our output and
    inspect it during debugging.

If a document comes in and there's no yaml frontmatter, we don't
jinjify.  You might not need any yaml frontmatter metadata but still
want jinja features (e.g. jinja macros).  In that case, add a dummy
var.

The reason for doing this is that legacy docs don't have any
frontmatter, and this is a convenient way to distinguish them.

 * Make -rXXXX versions for all builds, not just drafts
 * Add draft plugin
 * In template, set draft to trigger on both True and 'True'
 * Move path into PIPELINE definition
 * Silence some echo
 * Use .tex instead of intermediate_ltx
 * Simplify some bash
 * Let the plugin handle draft instead of passing it as an option
 * Cleanup .tex files

We can now do redacted and draft at the same time.

Refactor the jinja rendering and the redaction as a pipeline of
filters that run as needed.

It works, but needs some cleanup and documentation