`MocoJointReactionGoal::setWeight()` overrides `MocoGoal::setWeight()`

[nickbianco]

MocoJointReactionGoal::setWeight() inadvertently overrides the base class method MocoGoal::setWeight(). We should rename the method to MocoJointReactionGoal::setReactionWeight() or something similar to avoid ambiguity.

Reported on the Moco forum.