refactor base interface and classes,
  rename DataFormatAdapter to SchemaMapper
  rename TargetEntity to baseSchemaMapper
  extract BaseExchangeObject from TargetEntity
update .gitignore
remove BaseExchangeObject methods from SchemaMapperInterface
minor dev environment changes
  include Example/src in composer.json autoload
  update bin/data-exchange
  add TODOs
remove stale unicodify function from DataExchange\Common
remove psr4 autoload configuration from composer.json
  and specify versions for symfony cli and json-schema
remove BaseExchangeObject and introduce Record
update SchemaMapperInterface and update BaseShemaMapper
remove deprecated DataExchange\Common
  all the functionality is in Record
update ExportCommand as per refactoring changes
  introduce BaseCommand and DataExchangeApplication
Add example implementation and update bin/data-exchange and composer.json
remove depricated Symfony/Console methods from DataExchangeApplication
add an Example implementation of DataExchange