Module restructure

[DoganCK]

Closes #269

• [x] Removal of duplicate modules (such as ContinuousDistribution module under Continuous.fs) (this is a breaking change)
• [x] Removal of files that are not referenced in the fsproj files (e.g. FSharp.Stats/SpecialFunctions.fs)
• [ ] Addition of Distribution Parameters to the Distribution interfaces

The last item proved to be more complicated than anticipated. For instance MultiVariateNormal distribution has differently typed parameters (i.e. vector and matrix). This requires more thinking. This is also something we can discuss when we discuss the abstraction of distributions.

[codecov-commenter]

Codecov Report

Merging #270 (7268bcd) into developer (12bcd34) will decrease coverage by 0.01%. The diff coverage is 86.04%.

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@@              Coverage Diff              @@
##           developer     #270      +/-   ##
=============================================
- Coverage      48.18%   48.18%   -0.01%     
=============================================
  Files            153      152       -1     
  Lines          15514    15502      -12     
  Branches        2005     2005              
=============================================
- Hits            7475     7469       -6     
+ Misses          7479     7473       -6     
  Partials         560      560              

Impacted Files	Coverage Δ
src/FSharp.Stats/Fitting/GoodnessOfFit.fs	0.00% <0.00%> (ø)
src/FSharp.Stats/Testing/TTest.fs	78.57% <60.00%> (-5.81%)	:arrow_down:
src/FSharp.Stats/ConfidenceInterval.fs	100.00% <100.00%> (ø)
tests/FSharp.Stats.Tests/Distributions.fs	92.94% <100.00%> (ø)
...ests/FSharp.Stats.Tests/DistributionsContinuous.fs	100.00% <100.00%> (ø)
tests/FSharp.Stats.Tests/Fitting.fs	95.12% <100.00%> (ø)