Onion: multilayered concentric sphere and ellipsoid shapes (#333)

Adds new shapes `onion` and `onion_ell` (#293), including new tests, documentation, images, etc. Other changes:
- specifies `coated2` as deprecated shape
- updates the default value of `MAX_NMAT` to 60
- MAX_N_SH_PARMS is now calculated directly from MAX_NMAT, but extra check for its sufficiency is added to PARSE_FUNC(shape)
- Use of MAX_NMAT is now more informative in various help strings (`-h m` and for new shapes) due to use of new macro TO_STRING(A)
- overall extends the testing framework with Bash scripts in `tests/equiv`:
  - adds several new functions
  - moves common parts to a new file common.sh
  - comparison of shape files now ignores differences in shape names (if it is expected)
  - adds processing of exit codes and possibility to stop on the first error
  - increases refractive indices, adds -grid 16, but balances this with -eps 1 (keeping the computational time approximately the same)
- makes `tests/2exec` less stringent for "-int igt 3" (due to improvement of corresponding routines since 1.4.0)
- adds hints on inserting SVG files into MS Word in svg_images.txt
- adds specific note about an interim version of the manual
- increments ADDA version to 1.5.0-alpha2

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Co-authored-by: Maxim Yurkin <yurkin@gmail.com>

devtools/svg_images.txt

@@ -16,4 +16,14 @@ then set the width to 400 (field to the left of the icon).
 5) Save the file using "Plain SVG" as format (not "Inkscape SVG" for compatibility).
 
 6) Close Inkscape. You will get a warning "The file was saved with a format that may cause data loss" (due to the
-chosen format above). Ignore it and press "Close without saving".
+chosen format above). Ignore it and press "Close without saving".
+
+
+Related issue is use of SVG files in MS Word. While some support of direct import of SVG files have been present since
+version 2016, it is not perfect (especially if PDF is further produced from this file) and the imported images take much
+more space inside DOCX file.
+
+The solution is to use (once) version 2021 or later, where it is possible to convert SVG into EMF during import (for 
+instance, using Paste Special for object copied from inside Inkscape). The quality of the conversion seems to be very 
+good (including after saving as PDF), and the objects take even less space than the original SVG. Moreover, this object
+can further be used (copied) in earlier versions of Word.