Francois Brun / ctools

…lementing missing information from user parameters.

…oid code duplication in cscripts.

…ag in the execute() method.

Added ctool::require_inobs_nocube() method that throws an exception if a counts cube has been specified as inobs parameter. This method is then used by ctbin, ctexpcube, ctpsfcube and ctbkgcube.

…in case that those are not provided in the event list.

We cannot use the ctool base class for the Python scripts as this is an abstract class an Python does not know the concept of abstract classes. Hence for Python we need a real class to derive from, which we implement by adding the cscript class to the ctool.i interface.

…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.

The ctool base class is now used in the ctbin tool. The get_ebounds() method has been moved to the ctool base class so that it can be used also in other tools. This reduces code duplication.