Implemented trace_inv_quad_form_ldlt.
Remove lots of unnecessary code duplication using boost::enable_if magic.
Fix multi_gp_log call to trace_inv_quad_form.
Start adding more quadratic forms.
Simplify trace_inv_quad_form_ldlt code.
Implement agrad/rev version of quad_form.
Add inverse_spd function to math/matrix.
Add trace_quad_form and trace_gen_quad_form
Use trace_quad_form in multi_normal_prec.
Comment out currently unsupported (trace) quadratic forms.
First cut at the matrix_normal distribution.
Resolve conflict.