Some fixes for Justin's problem

1. Fixed a bug in the finite differencing of array inputs when they are in a vartree. The manual callback execution needed to be performed on the basevar instead of the vartree leaf.

2. Fixed a bug in array_helpers that cropped up while taking a derivative with respect to an integer array in a variable tree. These are non-differentiable, but OpenMDAO wasn't giving the right error.

3. Cleaned up the "oddball"directory from the save-load tests.