remove Maybe and MaybeVector

[alfredclwong]

fixes #160

[codecov-commenter]

Codecov Report

Merging #165 (5ff29a7) into main (c2e3101) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main     #165   +/-   ##
=======================================
  Coverage   50.76%   50.76%           
=======================================
  Files          66       66           
  Lines        6467     6467           
=======================================
  Hits         3283     3283           
  Misses       3184     3184           

Impacted Files	Coverage Δ
src/Examples/docs_examples.jl	0.00% <0.00%> (ø)
src/Geometry/Ray.jl	43.75% <ø> (ø)
src/GlassCat/sources.jl	0.00% <0.00%> (ø)
src/OpticSim.jl	88.88% <ø> (ø)

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