Eirik Hatlen / ctools

…lysis when using on-axis observations

…cripts now from csobservation instead of cslikelihood since they do not use proper optimizers.

The scripts cslightcrv, csphasecrv, cspull, cssens, csspec, cstsdist, and cstsmapsplit now have a "statistics" parameter to allow setting of the optimizer statistic. Except of cstsmapsplit, all of the scripts now derive from the cslikelihood base class.