Simplify configuration

[carlhiggs]

Refinement of region configuration is a priority, on several fronts:

• using a defined schema, against which user configurations can be checked with useful feedback supplied (Implement schema for current configuration file #506)
• using consistent and standardised metadata for inputs (Data sources should share consistent metdata record types/entries in configuration #472)
• allowing flexibility of approach to configuration (Add optional approaches to region configuration (XLSX template, GUI) #414)

Updating the approach to configuration will ultimately result in breaking changes to code for existing configuration files, although potentially some helper processes for 'translating' configurations to the newer format may be possible.