before default rotor center was shared among wind farm models, i.e. wakedeficit model of last instance was applied to all instances

renamed GCLDeficitLocal to GCLLocalDeficit
renamed NOJDeficitLocal to NOJLocalDeficit
made NOJLocalDeficit subclass of NiayifarGaussianDeficit to reuse k_ilk function
add tests to test_deficit_models.py

fix condition to determine if two wt are the same. Before dw and hcw should be 0 but with rotor average models, hcw may be gt 0

add function to create XRSite from simulation_result.flow_box() allowing precalculated sites including effects of neighbouring farms