Active mutation changeover

Some mutations seem to work better as active ones.  Let's get things
moving.
Tweaks & bugfix

This teaks a few things, adds a very important TODO (active mutations
are Exploitable without it) and fixes #8959.
Carnivore nutrition

KarmaChimera and Grizzlyadamz made a good point on the IRC: tough to get
Healthy food for Carnivores.

This helps take the edge off total vitamin dependence, since obligate
carnivores in the wild seem to live reasonably non-diseased lives.
Gets active mutations charging properly

Porting was straightforward once I had some time to sit down and grapple
with it.  Thanks for the start-off pointer, Kevin.
Clean up unused code

So far as I can tell this would never actually get reached.  :-/  Sorry,
BeigeSand.
Activates Vine Sprouter

As implied in the description, you can now make long-rope equivalents
pretty much at will.  Costs 10 nutrition/thirst, and vine-descending is
synchronized therewith.

Plant people with IT and MI are now pretty much the best damn vehicle
folks around.
Merge pull request #8962 from KA101/activemut

Active mutation expansion/bugfix