Basic engine

[florentLutz]

Is your feature request related to a problem? Please describe.
Students and researchers are sometimes asked to evauate configuration with engine for which they know very little about and for which they know existing models inside the FAST-OAD framework won't work. All they know are an sfc or max power in certain conditions.

Describe the solution you'd like
A generic wrapper for an engine for which only very basic figures of merit like an sfc, or power density which could be assumed constant throughout the flight

Describe alternatives you've considered
Usually it is done by leveraging the k_sfc tuning parameters but it is more tedious