Create a new config with defaults.
Private
_classPrivate
_defaultsPrivate
_sectionPrivate
_classGet data from the Section with our classname, if available.
If we have no classname, get all of the data in the Section
Set a config value.
Uses the Jupyter Server API.
The promise is fulfilled on a valid response and rejected otherwise.
Sends the update to the server, and changes our local copy of the data immediately.
Configurable object with defaults.