The images for the JOSM toms plugin are generated by invoking: ./make_images in a bash shell terminal window from this directory.
On a Windows PC, this will require the installation of Cygwin. All platforms (Windows-Cygwin, Mac-OS, Linux) require that
Inkscape has been installed, and its command-line invokation is on the user's PATH.

make_images assumes that both josm/ and openseamap/ are in the same directory.

Running make_images will overwrite existing images of the same name, but will leave all others untouched. If an image file becomes
obsolete, it must be deleted manually. This allows for images unique to the plugin to co-exist in the directory.