array distribution not respecting hard limits on parameter

[pkienzle]

In sasmodels.sasview_model.SasviewModel._get_weights the array distribution values are returned directly as the weights for the parameter regardless of what hard limits are set in the model definition file.

This is not a problem, since most models that have hard limits also have a test for VALID that keeps the parameters within the hard limits.

Note that the weights.ArrayDistribution class does respect the hard limits when returning the distribution, but this is not used in the SasviewModel._get_weights method, so the fix should start there.