docs: Have a smaller version of the STC shapes figure in SC/21.

The original appears not to scale in the HMTL, normally requiring
panning to view it all.  A smaller version created last week had
broken lines for the outlines.  This has thicker lines that remain
unbroken.
docs: Make the two images in Figure 21 of SC/21 the same dimensions.

This makes for easier comparison and looks better.
docs: Add three more items to the Glossary of SC/21.
docs: Expand and correct the pipeline sections of SC/21.

This includes a paragraph on logging and a few typo fixes by MJC.
docs: Add a "How to get help" section to SC/21.

This is a table of items like findme, showme, and ? paramater
prompts.

MJC contributed adjustment to the column widths to avoid the final
usage wrapping and to give more room for the descriptions, reformatted
the source for improved readability, added typography and corrected
typos.
docs: Add some explanation to Appendix A.3 in SC/21.
docs: Improve the Troubleshooting section of SC/21.
docs: Correct the quoting style in SC/21.

Distinguishes file listings and output from entered commands.
docs: Improve SC/21 section on solving configuration-file problems.
docs: Adjust space in SC/21.

Tweak some figure sizes and move locations, and modify some of the gaps.
docs: Tidying Chapter 8 of SC/21.

Revert to step numbers, add a tip noting the shortened name of
the PICARD recipe FAINT_POINT_SOURCES_JACKKNIFE, and use the correct
output NDF name from MOSAIC_JCMT_IMAGES, and miscellaneous small
changes.
docs: Tidying Chapter 9 of SC/21.
docs: Residual tidying in SC/21.
docs: Reword the ORAC-DR logging options in SC/21.
docs: Replace two SCUBA-2 array figures by a composite in SC/21.
docs: Modify the makefile for changes to graphics files in SC/21.

This relates to 265d746d8abea.