add "spline" method option in FugaDeficit and FugaYawDeficit

py_wake/deficit_models/fuga.py

py_wake/tests/test_deficit_models/test_fuga.py

...Zi=00400Zeta0=0.00E+00/D080.0000_zH070.0000_FIT9999UL.dat

...Zi=00400Zeta0=0.00E+00/D080.0000_zH070.0000_FIT9999UT.dat

...Zi=00400Zeta0=0.00E+00/D080.0000_zH070.0000_FIT9999VL.dat

...Zi=00400Zeta0=0.00E+00/D080.0000_zH070.0000_FIT9999VT.dat

...s/fuga/2MW/Z0=0.00001000Zi=00400Zeta0=0.00E+00/WTdata.bin

...s/fuga/2MW/Z0=0.00001000Zi=00400Zeta0=0.00E+00/WTdata.txt

...uga/2MW/Z0=0.00001000Zi=00400Zeta0=0.00E+00/inputfile.par

py_wake/tests/test_files/fuga/v80_deflection_x.csv

...ake/tests/test_files/fuga/v80_wake_4d_y_no_deflection.csv

py_wake/tests/test_files/fuga/v80_wake_center_x.csv

py_wake/utils/fuga_utils.py

py_wake/wind_turbines/power_ct_functions.py