[Awaiting Review] Non Uniform grid first pass

[xtalax]

Implements the nonuniform grid along with SciML/DiffEqOperators.jl/#517

Periodic conditions on a nonuniform dimension fail at the moment, as they are significantly harder to implement for this case, please advise whether this is acceptable to push to a future PR

fixes #59
Adds a helper function get_discrete which returns a dict containing the discrete independent and dependent variables. This eases solution retrieval.

• Implement FD algorithms
• Tests - includes an inviscid burger's eq test
• Docs

[codecov]

Codecov Report

Merging #81 (6a318cf) into master (17f4cbf) will increase coverage by 6.67%.
The diff coverage is 91.01%.

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
+ Coverage   83.41%   90.08%   +6.67%     
==========================================
  Files          12       12              
  Lines         814      918     +104     
==========================================
+ Hits          679      827     +148     
+ Misses        135       91      -44     

Impacted Files	Coverage Δ
src/discretization/discretize_vars.jl	86.41% <81.48%> (-1.09%)	⬇️
...discretization/generate_finite_difference_rules.jl	95.23% <85.71%> (+12.10%)	⬆️
src/discretization/differential_discretizer.jl	93.91% <91.89%> (+7.66%)	⬆️
src/MOLFiniteDifference.jl	87.50% <100.00%> (+1.78%)	⬆️
src/bcs/generate_bc_eqs.jl	80.85% <100.00%> (+15.95%)	⬆️
src/discretization/MOL_discretization.jl	85.00% <100.00%> (+8.30%)	⬆️
src/bcs/boundary_types.jl	97.93% <0.00%> (+2.06%)	⬆️
... and 3 more

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[ChrisRackauckas]

Looks like tests fail?

[ChrisRackauckas]

Looks like tests fail?