feat!: new variables in file conductor_definitions.xlsx

The new variables are:
    *MUTUAL_INDUCTANCE -> Constant value for the mutual inductance used if flag INDUCTANCE_MODE is set to 0.
    *SELF_INDUCTANCE -> Constant value used if SELF_INDUCTANCE_MODE is set to 0.

New flag values:
    *INDUCTANCE_MODE = 0 -> constant value from variable MUTUAL_INDUCTANCE
    *SELF_INDUCTANCE_MODE = 0 -> constant value from variable SELF_INDUCTANCE

BREAKING CHANGES
    *New variables MUTUAL_INDUCTANCE, SELF_INDUCTANCE
    *SELF_INDUCTANCE_MODE flag is used whatever is the flag INDUCTANCE_MODE
    *Default value for flag SELF_INDUCTANCE_MODE is changed to 1

modified:   input_files/input_file_template/template_conductor_definition.xlsx

Author: Mortara Alessandro