WIP feat: graphql schema for initial submission

• Mostly replicates the data model document with some corrections where it was inconsistent and a few changes discussed with @diversemix on a screenshare session
• Contains lots of questions as comments
• ! after a type means that field cannot be null (though in the case of strings it can still be empty)
• For arrays [Type!]! means it must be an array of non-null items but the array can still be empty, i.e. zero length
• Eventually part of this definition would be imported from pubsweet and we would only extend it with eLife specific fields

Out of scope

• agree and implement data model for consultation sessions and initial decision letter
• update current graphql definitions, resolvers and application code to use this schema