Changed Optimist to be more thematic and balanced.

Instead of a flat +20 to morale, Optimist now gives:

* All positive morale effects get a 25% boost.
* All negative morale effects are reduced by 25%.
* Permanent +4 morale (+5 after the boost)

This represents that optimism is less about always being happier and more
about focusing on good things while disregarding bad things.

Mechanically, the smaller flat boost means that you won't get a free 20%
boost to focus anymore.  This should give Optimist a distinct feel compared
to Fast Learner, rather than being a bigger boost under average conditions.