Creation of an empty new format calibration dataset

[vsmagalhaes]

This issue relates to the creation of empty calibration datasets under the new xarray DataTree paradigm.
This issues will probably entail the following, to be extended and revised:

• Revision of previous work on an implementation of the calibration dataset for the Fringe fit code.
• Re-utilization/ re-implementation of the fringe fit calibration dataset.
• Creation of a calibration dataset factory function that creates empty calibration datasets according to the schema and desired calibration type.