feat: refresh Connector API and Galaxy connector

Task TA-414 and TA-415

• Load connectors only once at app startup
• Update the Connector API to support new connector ID specification
  • Add support for author
  • Add support for root description in DataConnector
  • public params are renamed to shared params
  • DataObject are now called ExternalDataObject
  • ExternalDataObject now contains a dict of external accesses
  • Add file_extension in ExternalDataObject
  • A new instance method get_shared_parameters help retrieve a cleaned version of shared parameters
  • get_connection_parameters is now called get_connection_fields
  • CustomErrorException is replaced by four standard errors : ConnectionNotFoundError, AuthenticationError, UnreachableError, DataNotFoundError
  • get_connector_class returns a connector class from its unique id (for instance "madbot_api.connectors.madbot_galaxy.connectors.GalaxyConnector"
  • get_connector_instance returns a connector instance from its unique id and a dict of paramaters (shared and private all together)
• Update Galaxy connector