Negative lower bandwidth for Jacobi derivative

[jishnub]

Following https://en.wikipedia.org/wiki/Jacobi_polynomials#Derivatives, d/dx(P^(a.b)_n(x))=(..) P^(a+1.b+1)_{n-1}(x), so only one band should be populated
On master

julia> Derivative(Legendre())
ConcreteDerivative : Legendre() → Jacobi(1.0,1.0)
 0.0  1.0   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
  ⋅   0.0  1.5   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
  ⋅    ⋅   0.0  2.0   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
  ⋅    ⋅    ⋅   0.0  2.5   ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
  ⋅    ⋅    ⋅    ⋅   0.0  3.0   ⋅    ⋅    ⋅    ⋅   ⋅
  ⋅    ⋅    ⋅    ⋅    ⋅   0.0  3.5   ⋅    ⋅    ⋅   ⋅
  ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   0.0  4.0   ⋅    ⋅   ⋅
  ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   0.0  4.5   ⋅   ⋅
  ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   0.0  5.0  ⋅
  ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   0.0  ⋱
  ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋱

After this PR

julia> Derivative(Legendre())
ConcreteDerivative : Legendre() → Jacobi(1.0,1.0)
 ⋅  1.0   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅   1.5   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅   2.0   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅   2.5   ⋅    ⋅    ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅   3.0   ⋅    ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅   3.5   ⋅    ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   4.0   ⋅    ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   4.5   ⋅   ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   5.0  ⋅
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋱
 ⋅   ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅    ⋅   ⋱

[codecov]

Codecov Report

Base: 58.98% // Head: 58.98% // No change to project coverage 👍

Coverage data is based on head (a2f6fab) compared to base (4f2c6e4).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #96   +/-   ##
=======================================
  Coverage   58.98%   58.98%           
=======================================
  Files          28       28           
  Lines        2460     2460           
=======================================
  Hits         1451     1451           
  Misses       1009     1009           

Impacted Files	Coverage Δ
src/Spaces/Jacobi/JacobiOperators.jl	59.54% <100.00%> (ø)

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