Cleanup Multiplicative Parameters handling

[joaquimg]

1 - add protection against multiplicative stuff in cubics
2 - remove pure parameter multiplication tracker
3 - fix objective part of pure multiplicative parameters

With a little help from my friend, Claude.

[joaquimg]

@odow maybe before 0.15, so we do not need 0.16.

I'd be fine both ways.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.68%. Comparing base (29b419e) to head (86f96ac).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #224   +/-   ##
=======================================
  Coverage   99.67%   99.68%           
=======================================
  Files           9        9           
  Lines        1861     1902   +41     
=======================================
+ Hits         1855     1896   +41     
  Misses          6        6           

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