Replace server-side hard-coded English error messages

[elisee]

Both in superpowers and superpowers-game, we have various error messages sent by the server through callbacks that haven't been internationalized.

A couple examples:

• RemoteProjectClient.ts
• RemoteHubClient.ts
• SceneAsset in SupGame and most of the other asset classes

They should be replaced by localization IDs ("namespace:some.key"), added to the locale files and the client should run the IDs through SupClient.i18n.t(...). Even better, it should enclose them in a descriptive string like Could not create project: ${reason} which should itself be locazlized.

The localized reasons should be full sentences (maybe multiple) so they should end with a full stop.

[elisee]

Hmm, how do we deal with variable interpolation like here, since the localization happens on the client?

We should probably replace err: string with something like err: SupCore.LocalizedError and give it a constructor like new SupCore.LocalizedError("sceneEditor:errors.invalidActorId", { id }).

[elisee]

Started things off by adding the SupCore.LocalizedError class: caa6606