Simon Bonnefoy / ctools

…)-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.

- change evfile parameter to infile
- added irf and caldb parameters
- use pointer to GModel for test source
- clean exception handling
- minor code adjustments