[Feature Request] Add Warning About Trains at Edges

[krnyoshi]

Problem:

• TS crashed when trains were being recruited off map.

Reason:

• Unit with IsTrain=yes was placed too close to the map edge (refer to the attached screenshot where the sandy terrain area indicates where crashes happen).

Control:

• Infantry with followers were placed in the sandy terrain areas. Game did not crash when recruited.
• Vehicle with followers were placed in the sandy terrain areas. Game did not crash when recruited.
• Vehicle was given IsTrain=yes flag. Game crashed.
• A lone locomotive was placed in the sandy terrain area on a track. Game crashed.

Solution:
Warning on save when a unit with IsTrain=yes is placed too close to the map edge. Warning message will state that when the unit is recruited or if it is a follower, the game will crash when a team containing the unit/follower is recruited.