Extended IBioPolymerWithSetMods interface, changed hashcodes

[Alexander-Sol]

IBioPolymerWithSetMods is used as a dictionary key in MetaMorpheus. However, as it doesn't implement an IEquatable interface, equality comparison is done by reference, instead of by calling the Equals method (I think).

This PR adds the IEquatable interface to the IBioPolymerWithSetMods interface.

The HashCode methods for classes that implement IBioPolymerWithSetMods are still the same. This is fine, as the Equals method is used to make the final determination of what is and is not a unique entry in a dictionary.

[codecov]

Codecov Report

Attention: Patch coverage is 88.13559% with 7 lines in your changes missing coverage. Please review.

Project coverage is 77.23%. Comparing base (fed869f) to head (64a99ec).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...zLib/Transcriptomics/Digestion/OligoWithSetMods.cs	85.71%	1 Missing and 3 partials ⚠️
...roteolyticDigestion/PeptideWithSetModifications.cs	91.30%	0 Missing and 2 partials ⚠️
mzLib/Proteomics/Protein/Protein.cs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #811      +/-   ##
==========================================
+ Coverage   77.21%   77.23%   +0.02%     
==========================================
  Files         218      218              
  Lines       32964    33014      +50     
  Branches     3413     3422       +9     
==========================================
+ Hits        25453    25499      +46     
+ Misses       6944     6942       -2     
- Partials      567      573       +6     

Files with missing lines	Coverage Δ
mzLib/Omics/IBioPolymer.cs	0.00% <ø> (ø)
mzLib/Omics/IBioPolymerWithSetMods.cs	98.68% <ø> (ø)
mzLib/Transcriptomics/NucleicAcid.cs	93.00% <100.00%> (+0.92%)	⬆️
mzLib/Proteomics/Protein/Protein.cs	95.41% <75.00%> (-0.29%)	⬇️
...roteolyticDigestion/PeptideWithSetModifications.cs	95.88% <91.30%> (-0.05%)	⬇️
...zLib/Transcriptomics/Digestion/OligoWithSetMods.cs	87.55% <85.71%> (-0.24%)	⬇️

... and 1 file with indirect coverage changes