- Fixed output location of exports from Inkscape (was current location, now ...

IMGDIR).

- Extended targets of various rules. ...

- Added pdfcrop to SVG processing chain (experimental).

- Added new makefile infrastructure for general documents. ...

- Created include files for various "standard" items (paths, rules, etc.).
  These will ultimately be used by all the other make include files in
  order to promote standardisation and consistency.
- Removed obsolete Perl script for handling document includes.