Change: Improve handling of excessively large StructureIdx values

[leezer3]

Closes #185

Needs some more testing to make sure nothing has broken.

Specifically:

• Test what happens when an object indices is declared twice. ==> Broken, see below.
• Double-check routes using .Crack and the other deformable object types.
• Do we port to Route Viewer? New: Basic route viewer mode for the main program #165 may negate the need for this, but not sure how far away that is.

[leezer3]

Fiddle, some of the Travis builds are failing because using as an inline out isn't actually supported until C# 7.0, despite the fact that this is just a syntatic little push....

Will fix that, and probably port to Route Viewer later.

[leezer3]

Hmm.
Object indicies declared twice now throw an exception (Object containing the same key has already been added)

This is not logged anywhere either, which isn't good, and wasn't before this was started either.
Current behaviour is to always overwrite with the new object.

TODO:

• Implement our own dictionary class, allowing us to override the Add method (Probably requires the least amount of work ( https://stackoverflow.com/questions/6250706/override-dictionary-add )
• Log the fact that an object index has been used twice- This may increase error counts slightly on some routes, but it's worth it.
• Check BVE2 & BVE4 behaviour on this front. BVE2 / BVE4 both overwrite the object with that most recently loaded & generate no errors.