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

Implemented wake_radius() function for the different wake models and modified args4turb to be independant from deficit

add selfsimilarity blokage model
prepare for gradients
New structure. Old WakeModel mainly in new EngineeringWindFarmModel
add deflectionmodel
update documentation

Prepare for iterative calc_wake backend by adding an the source-wt dimension(i) to all calc_deficit arguments

deleted test_examples.py as all example modules are tested in test_main.py