Added birth-death kerel with ability to specfify which kernel with CT_KERNEL
use State::view_lookup to get pointer to current view
give transition_feature_{0,1} more descriptive names

transition_feature_{gibbs,mh}
WIP
add mh_choose to aid in modifying mh kernel
simplify mh column transition operator with mh_choose helper
merge master in for testing
BUGFIX: don't double free
resolve merge conflicts