Incubator: Add thermal mass to "Test Preemie"

[RobertLRead]

This is a simple crafty skill. The current "Test Preemie" doll is made of little plastic pellets. They are both insulating and have no thermal bass. It is very difficult to heat them in a meaningful way.

We need to creating a little 1 kilogram mass of water, or something other material, that will moderate temperature changes. In essence we are attempting to model human flesh.