Support conversion to numeric type for nested dictionaries

[rafmudaf]

Support conversion to floris_float_type for values in nested dicts

FLORIS has the type_dec.floris_numeric_dict_converter function to cast data in an input dictionary to the type_dec.floris_float_type data type. However, this function is not recursive, so it only converts the first level of data in the dictionary hierarchy. Because of this limitation, there's a workaround in the Turbine-class init when loading the multidimensional Cp and Ct tables, and another one is incoming in #832.

Proposed solution

Support a recursive numeric type cast in dictionaries.

Alternatives considered

More workarounds, but things are getting complicated.