Validate characters in SpawnNamed names

[rogeralsing]

We don't do any validation at all of the name passed to Spawn.
We should probably prevent the use of things like / as that is used when creating child names.

[stuartcarnie]

👍 what would it look like? Would a valid language identifier suffice? No operators, #, :, |, and so on?

[rogeralsing]

And let's not forget about our non latin alphabet users. e.g. it should still be possible to name your actors in Mandarin if you want.
Lets just focus on control characters