Updated the yaml doc with the OneToMany relation

[tseho]

I added to the Yaml documentation how to set the OneToMany relation between an entity and his translation entity.

[jvandesande]

@tseho the relations that you added are automatically added by the YamlDriver, so they shouldn't be added in the Yaml file.

[tseho]

@jvandesande Ok. In my case, for some reason, I wanted to manually define the relation in my entities. But I forgot the "indexBy" option ... which is stupid when you use the indexBy stragery. I know. So after loosing some time on it, I tought it could be nice to add an example of how to do it in the documentation.

Maybe, if I add something like this: "If you don't want to use the generated relations and want to define yours...". Could it be better ?

[jvandesande]

@tseho That would be better, thanks.

[tseho]

@jvandesande done.

[jvandesande]

@rjbijl @sandermarechal could you check/merge this.

[sandermarechal]

Looks fine, thanks!