Train buying interface could use a lot of improvement

[michaeljb]

• fewer clicks?
• make it more obvious if shares must be issued / implications about issuing those shares
• button to explicitly start selling player shares?
• show all available trains, grey out/etc trains that may not be bought, for whatever reason
• confirmation if buying train from another player

[michaeljb]

latest idea - view enhancements that wouldn't need to change actions

• list of trains, better grouped by owner than now
• click a train to get a view describing what needs to be done to pay for train
  • corporation cash? issue shares?
  • president cash? sell shares? loan?
  • "cannot afford, must buy cheapest train" etc