Sigmoid Activation function implementation with simplified batch calc…

[crapxxi]

…ulation

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new algorithms include a corresponding test class that validates their functionality.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.18%. Comparing base (a0c3eb5) to head (03b0fb8).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7609   +/-   ##
=========================================
  Coverage     81.17%   81.18%           
- Complexity     7852     7863   +11     
=========================================
  Files           828      829    +1     
  Lines         24865    24885   +20     
  Branches       4849     4855    +6     
=========================================
+ Hits          20184    20202   +18     
- Misses         3909     3910    +1     
- Partials        772      773    +1     

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[alxkm]

Thanks for the contribution - checkstyle is clean, the build is green, and
shipping tests with the implementation is appreciated.

Two small things before merge, both noted inline.

[alxkm]

Looks good. Thank you for the contribution.