More WIP; most of the tests passing now
WIP: Fixed some issues with rotation models and with composite models (still need to tweak those though)
This takes care of a few more of the tests by setting the parameters properly.
Well this is a bug...
The _validate_lam function required model.mu to be set, but that's not necessarily the case when this is called from within the model's constructor and vice-versa for _validate_mu.  This should take care of it by making sure the parameter access raises an AttributeError and that that error is caught and ignored
As discussed in #980, rewrote Custom1DModel as a decorator that returns a class.
Fix some slight bugs in the handling of 2D rotation matrices
fix typo
col_deriv should be false for polynomial models; let's also make this a class attribute along with linear
Fix up how some of the projection models were using their parameters in computations.  For example gamma shoud be used in its raw (radians) units.