Add a flag to disable adding margins to sprites with spacing

[SnowyMouse]

This behavior is inconsistent and smells way too much like a hack done by the original developers, since an image editor can be used to achieve the same thing (similar to the blur and sharpness filters). However, it is required for stock sprites to work correctly (notable HUD numbers).

Therefore, there should be some sort of a flag to disable this behavior. However, changing existing tag definitions has always resulted in problems later down the line, notably with extracted tags.

[Aerocatia]

As of MCC tool.exe (and current invader) the stock game can control the spacing by editing the spacing value in the tag.
This is not exposed in invader-bitmap however.