Feat: manage without translations

[thebiggianthead]

This PR adds the ability to override the default of disabling the "manage translations" button when no translations exist as yet. This helps to solve scenarios where translated documents already exist but they need tying together on the metadata document.

To review:

• Is the config name allowCreateMetaDoc OK? I'm not totally happy with it but my creativity is letting me down.
• Test different scenarios and that the button works as expected when the option is disabled / enabled and whether the metadata doc already exists or not.

[SimeonGriggs]

The idea and config option look fine to me. If you've tested this works as expected, then go for it.