Better dispatch on evaluations

[dehann]

This and all related ::AbstractArray{<:Real}, also towards AD, e.g.

julia> p1(-2:0.1:2)
ERROR: MethodError: no method matching (::BallTreeDensity)(::StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}})
Closest candidates are:
  (::BallTreeDensity)(::Vector{Float64}) at /home/dehann/.julia/packages/KernelDensityEstimate/Kx5zN/src/DualTree01.jl:438

julia> p3(v')
ERROR: MethodError: no method matching (::BallTreeDensity)(::LinearAlgebra.Adjoint{Float64, Matrix{Float64}})
Closest candidates are:
  (::BallTreeDensity)(::Vector{Float64}) at /home/dehann/.julia/packages/KernelDensityEstimate/Kx5zN/src/DualTree01.jl:438