When saving ship, save by default to its own folder

[royal holly]

I use subfolders for my ships and often save new versions into the wrong folder, because the working folder changes when you open a different ship, etc.

Also a slightly more ambitious variation:

"Save ship design" just overwrites the previous file, and there is a separate "Save ship design as..." option.

[minor sorrel]

I think its gonna be something like ctrl+H or something like that