[Rails-devel] More 18AL features

[Erik V. <eri...@hc...>]

On the way to a complete 18AL implementation, the following has been added:

- Bonus token removal on buying the first 6-train. 
For this purpose, a new interface Closeable has been created, 
that can be implemented by any object that can disappear at a phase change.
I'm considering to use it for private company closure as well.
- Only one train can be bought per turn, until the first 4-train is bought.
- Optional unlimited 4D trains (default=no).
- Optional delayed 4-train obsolescence (default=yes). Obsolete 4 trains are
displayed as (4).

Also added an 1835 feature: trains can be traded between companies from the
green phase only.

I think only the M&CR and NDY special properties remain to be done.

Erik Vos