U/gblackadder/pydantic and excel

[gblackadder]

Surrounding the json schemas is now a python library. The main purposes are:

1. Functionality to create pydantic classes for each of the main json schemas and then Excel files from each of the main pydantic classes
2. A Metadata Manager that helps users populate pydantic objects for a given metadata type
3. An interface to Excel allowing the pydantic models to be written to Excel, and previously written Excel metadata files to be read into pydantic objects
4. A folder of Excel files formatted for different metadata types

Future work is required to add versioning, so that pydantic classes for older json schemas are still available (ditto Excel files).

If the PR is accepted then we should ideally set up an action so that changes to the json schemas automatically cause new pydantic classes to be written if needed alongside new Excel files

[gblackadder]

Note that this is a defintion of keyword. And later on, when the definition is invoked, it is invoked as an array. So without this change we get an array of arrays of key words which we don't want. All we want is an array of key words