Add computation function for bounds and initialize bounds

[MaxenceGollier]

As discussed on zulip.

Solves your bug @MohamedLaghdafHABIBOULLAH

[codecov]

Codecov Report

❌ Patch coverage is 70.73171% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.62%. Comparing base (e0f214d) to head (ccdd7b3).
⚠️ Report is 206 commits behind head on master.

Files with missing lines	Patch %	Lines
src/R2DH.jl	0.00%	5 Missing ⚠️
src/R2N.jl	0.00%	5 Missing ⚠️
src/LMTR_alg.jl	66.66%	1 Missing ⚠️
src/TRDH_alg.jl	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #240       +/-   ##
===========================================
+ Coverage   61.53%   84.62%   +23.09%     
===========================================
  Files          11       13        +2     
  Lines        1292     1620      +328     
===========================================
+ Hits          795     1371      +576     
+ Misses        497      249      -248     

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[MohamedLaghdafHABIBOULLAH]

Thank you @MaxenceGollier, have you tested while incorporating the changes in this PR?

[MaxenceGollier]

No, it works even without these changes (on the nnmf problem)

[dpo]

I still think it's important to initialize $\sigma = 0$ in the model in #239.