[1858Switzerland] Add entities, map, tiles, icons and logos

[ollybh]

Implementation Notes

1858 Switzerland is a new prototype from Ian D Wilson. As the name suggests, it is a game based on 1858 set in Switzerland.

This adds definitions of:

• The public companies (majors, 5-/10-share corporations).
• The private railway companies (implemented as a pair of a private and a minor).
• The trains and phases.
• The map.
• The tiles.

There's almost no actual code in this, just enough to override some of the definitions for trains and phases inherited from the base 1858 code.

It also adds SVG icons and logos for the companies, plus a few icons for the map.

Screenshots

Before clicking "Create"

• [x] Branch is derived from the latest master
• ~Add the pins or archive_alpha_games label if this change will break existing games~
• [x] Code passes linter with docker compose exec rack rubocop -a
• [x] Tests pass cleanly with docker compose exec rack rake