libvb/Constellation: refactor gradcost, and use it for steepest descent
tests/test_hypermap: try steepest descent if given -g flag
libvb/Minimizer: start templatizing (but so far only double)
libvb/Minimizer: A bit more generic
libvb/Minimizer: use minimize_qn, real algorithms work better
tests/test_hypermap: different defaults, normalization fails sometimes
libvb/Cube: make mirror display optional