Introduce generic alias conversion.

[discordier]

We need some generic way to create an alias from a raw value and a value from an alias.

[discordier]

@stefanheimes We should talk about this.

[zonky2]

@discordier was ist daraus geworden?

[discordier]

@stefanheimes alias aware branch

[zonky2]

https://github.com/MetaModels/core/tree/feature-aliasaware