No-op code & docs cleanups

[alyst]

These are rather trivial commits cherry-picked from #193 that don't change anything essential, but once they are in, it should be easier to manage the rest.

The changes are:

• code formatter whitespace fixes for the .md files
• move some using directives from the individual unit test .jl files to the parent .jl file
• in RAMSymbolic rename xxx_function to xxx_eval! as that better follows Julia naming conventions and should make the code a bit more readable (and shorter)
• cleanups to the fitmeasures that simplify some method signatures (remove unused type parameters).
  This is a bit less trivial set of changes than the rest, but in the end it does not really change how the functions are calculated.
  Except for switching p-values calculation to use ccdf(x) instead of 1 - cdf(x) -- this could potentially give more precise results for p-values close to 0.

[codecov]

Codecov Report

Attention: Patch coverage is 95.12195% with 4 lines in your changes missing coverage. Please review.

Project coverage is 72.82%. Comparing base (8b0f880) to head (c65c8a9).
Report is 16 commits behind head on devel.

Files with missing lines	Patch %	Lines
src/frontend/fit/fitmeasures/chi2.jl	93.75%	2 Missing ⚠️
src/implied/RAM/symbolic.jl	93.10%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #245      +/-   ##
==========================================
- Coverage   72.94%   72.82%   -0.13%     
==========================================
  Files          50       50              
  Lines        2218     2208      -10     
==========================================
- Hits         1618     1608      -10     
  Misses        600      600              

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