Use of overloaded and/or inverted objective functions for algorithms requiring minimizing vs maximizing of cost/score

[hellkite500]

Per @mattw-nws comment on #41:

Strongly believe we shouldn't change this/use the same name... can we instead add
"one_minus_kling_gupta": objectives.kge,
... and really, also change kge to be named one_minus_kge?
Alternatively, we could add code that detected a non-zero target whenever PSO was used, and automatically optimize for target - f(x) instead, issue a NOTICE, and then re-invert the value when we're outputting the objective scores to the user? This last part > would be important if we do "magic" like this.

We need to take some steps to address these issues.