Use IRDB defaults
This ensures that proper default values from the IRDB are used.
Some minor database changes are necessary.
The defaults are now instantiated as separate objects. This runs the risk of polluting the database with identical objects. However, this is already the case now, so not directly a problem of this merge request. MDBObjectMeta._find_existing()
is intended to prevent this, but it is currently disabled, see #210.
Also fixes some minor other problems like the CI failures and storing floats in FITS files.
To be done after this MR: verify that indeed calling ScopeSIM directly with all defaults will produce the same data as calling ScopeSIM through MicadoWISE with all defaults.