BugFix: serum traits research status should not be checked against their python declaration, but using the new is_trait_researched() function on the business object.

(cherry picked from commit fb450f01)

BugFix: serum traits research status should not be checked against their python declaration, but using the new is_trait_researched() function on the business object.

Added: new work goal Try This Serum (give a serum to a person who is not a family member or employee).
BugFix: minimum of 2 goals per category need to be enabled.
Fixed: new goals are autmatically added to existing games (old save games).

(cherry picked from commit 9f0ef499)

Refactored: remaining hash functions to match default implementation inclucing eq and ne

Refactor: serum_mod_core, treat serum_mod_list as set() which supports hash. When in future serums are defined in python only, we can scrap the stack crawler and declare all our serums in python too.

Removed old fix function.

Fixed: use change_stats function with named parameters to make clear what is changed.

Fixed: event tracking value should be set to min_value + 1, events might have been disabled and thus have a low count, on enable, they would trigger repeatedly after each other, we don't want that.