Lili Yang / ctools

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

The ctobservation::first_unbinned_observation() and ctobservation::next_unbinned_observation() methods implement an unbinned CTA observation iterator. Using this iterator avoids code duplication and generates a uniform interface for tools to loop over CTA events lists.

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 constructs have been replaced by the new logger methods.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

The building of a cuve on the fly raised issue with memory going out of scope. This is fixed by making the CTA event cube a member of ctbin, and having the cube() method returning a reference to that member

It turned out that the partial coverage of counts cube bins using the weighting array does not work. The problem is spill over of events from one RoI to another than can not be dealt with at the level of a stacked analysis. The old logic of using only fully contained pixel is put back into place. The weighting array is (for the moment) conserved as it could serve other purposes. However, excluding of pixels is already accomplished by setting a pixel value to -1, so it remains to be seen whether we would like to keep that logic or if we would like to use the weighting array (which is more universal).

The GCTAEventCube::map() method has been renamed to GCTAEventCube::counts() (#1789)

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.

Without the energy margin, roundoff errors may lead to the exclusion of the energy bin in case that a single energy bin is used.

…d in observation ebounds. Also added some improvements to csspec.