Modelzoo exporter command

Nobody has claimed this yet.

We need a command & API to export trained models into modelzoo format.

## Use cases
### Export SavedModelBundle method
- input: `SavedModelBundle` directory (including `variables`, `saved_model.pb`)
- input: additional needed parameters (inputs, outputs, data type etc.)
### Add missing information to existing YAML specification
- input: A ZIP file with a `SavedModelBundle` and a `model.yaml` file

## Goal

The exporter should be able to write the YAML specification and ask the user for missing parameters (like author names, a doi to the training data etc.).

## Existing code

Writing the model is already implemented in Noise2Void in Fiji and should move from there to this repository, then N2V and others can use `imagej-modelzoo` as a library: https://github.com/juglab/N2V_fiji/blob/master/src/main/java/de/csbdresden/n2v/train/ModelSpecification.java

Tagging @esgomezm @ctr26 in case it might be possible to reuse code from DeepImageJ for the UI part (discussion started in [this issue](https://github.com/deepimagej/deepimagej-plugin/issues/15)). @tibuch

Start by reviewing the existing ModelSpecification.java implementation in N2V_fiji and the linked DeepImageJ UI discussion. Determine the API and command boundaries for SavedModelBundle and ZIP inputs, including missing parameters and YAML output. Done means a decided, reusable exporter design that supports the listed use cases.

Written by the indexing model from the issue text.