feat: save sound composer project

[ansaminard]

Added the possibility to save a sound composer project (.scn file) in class SoundComposer
To allow this, it was necessary to modify class Filter such that it now stores the FRF

Also, SourceControlTime and BBN and harmo sources were modified such that the "displayed string(s)" in Sound Composer project files can be stored and retrieved in load/save operations.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (437145b) to head (6c31804).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main      #248    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           81        81            
  Lines         4867      4968   +101     
==========================================
+ Hits          4867      4968   +101     

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[a-bouth]

Looks good to me but don't forget to add plots to the general description of your PR

[ansaminard]

Looks good to me but don't forget to add plots to the general description of your PR

@a-bouth There is no plot to add