Add command to export all EXPRESS schemas (*.exp) without annotations

[ronaldtse]

e.g.

$ suma extract-express -o express-files -a additional-schemas.yml [metanorma-srl.yml]

Results:

express-files/
+- business_object_models/
+- core_model/
+- domain_models/
+- resources/
   +- action_schema/
      +- action_schema.exp

The *.exp files are defined in:

• resources come from metanorma-srl.yml
• business_object_models, core_model, domain_models are developed outside the SRL/Metanorma, and we need to find a way to list them. Maybe an additional schema listing file.

Zipping:

$ suma extract-express -o express-files.zip -a additional-schemas.yml [metanorma-srl.yml]

Results:

express-files.zip

Which extracts out the above structure.