Separate submod name (identifier) and display name (user-friendly display text)

[dreamscached]

As of now, the only displayable identifier is submod name, which is limited to a range of alphanumeric + spaces; this confuses submod creators and sets an obstacle in a way of properly naming the submod (e.g. adding ' to the name or other characters.)

As @Booplicate mentioned on Discord, it could be a good change if we separated the ID and display name.

If a display name is not defined, submod menu would fall back to its identifier. That way it should be pretty much backwards compatible and should not affect existing submods in any way.