Leonardo Di Venere / ctools

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

Since the new GApplication logger methods are more compact than the old format the "logTerse()" etc. constructs have been replaced by the new logger methods. At the same time, the chattiness levels have been reviewed with the following behaviour:
- TERSE: only headers
- NORMAL: standard output, only main results or computations
- EXPLICIT: detailed output
- VERBOSE: verbose output, mainly for diagnostics

"fit" is more appropriate for the tool as the tool itself is not refitting (it's a "refit" of a ctlike result).

According to a study by Stephan Fegan done in the context of Fermi/LAT analysis, the best way to determine a butterfly diagram is to draw the envelope of the error ellipse of the model parameters. I implemented this method now in ctbutterfly. I also changed the output file, having now two columns giving as function of energy th minimum and maximum intensities.

Conflicts:
	examples/show_butterfly.py

…(see #1360 for details).

…)-function of individual ctools