Extend data generation to models that reach outside themselves for model objects about openmx HOT 5 CLOSED

This commit d31aa76 should make this work. However,

1. @tbates please test this. When I ran the first umxACE help page model, it worked great but I haven't tested it against all the umx models.
2. This code seems to pass all tests on my machine, but I'm concerned that we are not testing everthing related to data generation particularly with (a) state space models and (b) relational/RAMPart models. @jpritikin could you do some testing with this (assuming the nightly tests pass)?

from openmx.

I'll run some tests on umxCP, umxSimplex etc. and add this as an example to umxACE

from openmx.

Nightly tests passed so I guess things are in good shape. I'm not sure what else to test. All tests that I've written are part of the test suite.

from openmx.

I'll check it on a multilevel BG model and a 3- or 4-level model I've used before. I'm nervous when things seem to work this easily ...

from openmx.

It's probably done.

from openmx.