Leonardo Di Venere / ctools

The Crab test event data are now derived from the Prod2 South_0.5h IRF with an offset angle of 0.5 deg and a simulation radius of 3 deg.

The outcome of the unit tests depends on the presence of the CTOOLS environment variable. If the CTOOLS environment variable is not present the unit test should fail, otherwise it sould succeed.

The pars() methods allow to assign or to retrieve all application parameters in a dictionary. Makes ctools a bit more "Pythonic".

This led to an invalid pointer problem before, is now fixed due to GammaLib fix.

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 constructs have been replaced by the new logger methods.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

See #1823.