more mutations to mutant starts, TCL mutant, lock behind threshold achievement

[anoobindisguise]

Summary

Content "additions to mutant scenarios"

Purpose of change

The list of available mutations in mutant starts could be expanded to include more entry level mutations, there was no "TCL mutant" start, and mutant starts are a good candidate for meta progression.

Describe the solution

TCL start split into TCL staff and TCL subject, TCL staff has the Lab professions + security guard. Subject has the mutant starts.

Experiment and TCL subject are locked behind the "go post threshold" achievement, any threshold works for this. But you'll have had to mutate some first before making a mutant at char creation. Previously mutations being too advanced was part of Kevin's objection to a similar version of this PR I submitted in the past so hopefully this will help make things more workable.

Added the following mutations: "ANTENNAE", "HORNS", "THICKSKIN", "THINSKIN", "LIGHTFUR", "SCALES", "PAWS", "NAILS", "SHELL".

Describe alternatives you've considered

If you have any other suggestions for this intro mutant list please suggest them here! I tried to ensure it's only starting-level mutations. Note that there is an issue with stat-adjusting mutations, these do not play nicely with character creation due to adjusting those stats during creation.

Testing

Compiled+confirmed functional.

Additional context