Leonardo Di Venere / ctools

All likelihood ctools now derive from the ctlikelihood base class. This avoids code duplication and provides all likelihood tools with a uniform interface.

(still need to remove some debug statements later)

…served events in ctlike.

…erLM logger constructor interface (now takes a pointer instead of a reference).

…(see #1360 for details).

…)-function of individual ctools

…d scave() methods to ctool interface. Add read_ahead() method to handle reading of task parameters at the beginning of the task execution. Remove all m_read_ahead members from the derived classes.

…esponse for all CTA observation in the container that have not yet a response using the task parameters.

…bservation::hasresponse()