Allow the user to upload Information Extraction labels

[DerKernigeFeuerpfeil]

Is your feature request related to a problem? Please describe.
I want to use refinery to label for information extraction, but cannot upload my existing labels, which sets me back in my project by a large margin.

Describe the solution you'd like
I want to tokenize my data in a notebook with the same tokenizer that refinery uses. I would then match the labels to the respective tokens. Technically, this would be realised through a JSON attribute, e.g. label__headline__MANUAL with the key of that being a list with one label per token, e.g. ["0", "0", "PERSON", "0"] (the "0" could also be null or anything other that is specified in the docs). This data, I want to upload to refinery. During the tokenization process, I want refinery to tell me if the internal tokenizer and my pre-tokenized data does not match. If so, there are two levels of complexity I can imagine:

1. simple: it should stop the tokenization process and throw an error that the tokenization did not match my pre-provided tokens (in length)
2. medium: it should additionally tell me what record caused this and what the tokenization lengths were (e.g. refinery produced 200 tokens while I only provided a list of 193 tokens)

Describe alternatives you've considered
hacking the project import/export functionality, which is rather complicated.

Additional context