Mathieu Servillat / ctools

…alues to the vector when called several times)

…(see #1360 for details).

…)-function of individual ctools

Conflicts:
	ChangeLog
	NEWS

As the GCTAObservation class now handles transparently the disposal and re-loading of information it is not needed anymore to re-load the event list upon call of the obs() method. We thus can put the obs() method inline as before.

The memory needs for ctobssim have been reduced by first working on a local copy of the CTA observation (this de-allocates properly and memory cache associated to the response functions), and by saving and disposing the event lists immediately if called using the execute() method (this is the method called when the tool is run from the command line).

…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.