Iftach Sadeh / ctools

ctexpcube was in fact executed twice due to a bug in the main.cpp file.

So far any exception occuring during the construction of the ctools were not catched. This is corrected now.

(still need to remove some debug statements later)

The publish parameter has been added to the following tools:
- ctbin
- ctbkgcube
- ctcubemask
- ctexpcube
- ctmodel
- ctskymap
- cttsmap

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.

… GCTAExposure to GCTACubeExposure and GCTAMeanPsf to GCTACubePsf).

…(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.