Modify CreateGeneOntologyTags.py to generate json

This strips out the OMERO dependency from the @will-moore's script. The new workflow is:

```
python CreateGeneOntologyTags.py ./gene_ontology_tags.txt > go.json
# If you have jq installed, you can format it with:
# python CreateGeneOntologyTags.py ./gene_ontology_tags.txt  | jq . > go.json
bin/omero tag load go.json
```
Any suggestions on where the best place for something like this to live would be? As part of `bin/omero tag`?

/cc @will-moore @manics @pwalczysko @ximenesuk