Simon Bonnefoy / gammalib

The attribute for identifiers is "id". This has been corrected in GCTAModelBackground. Further, writing of the attribute has been added to GModelSky. Attributes are also only written if the identifier string is not empty.

(I chose `centre` because there were more `centre` than `center`
around.)

The coding and design conventions (CDC) document was also updated.

Conflicts:
	doc/source/user_manual/modules/model.rst

Fix some unimportant compiler warnings to have a clean build.

I ran this build:
CXXFLAGS="-Wall -Wno-c++11-long-long -pedantic -std=c++98" ./configure
make -j 1

This commit fixes the few compiler warnings that showed up (all unimportant).

There is no way to fix the issue that `long long` is not standard C++98,
but it's an extension that has been supported by most compilers for a decade,
so it's OK to ignore:
http://stackoverflow.com/questions/4017621/how-to-do-portable-64-bit-arithmetic-without-compiler-warnings

Conflicts:
	inst/lat/test/data/p7v6/crab_model.xml

The usage of the gammalib::reduce(chatter) function led to blank lines. Now we check if we're higher then TERSE before calling the print() methods with gammalib::reduce(chatter).

…omatically detected King profile PSF upon IRF loading.

A unit test was added to verify that the King profile PSF is normalized correctly. For this purpose a King profile PSF calibration was inserted in slot 2 (bcf/000002) of the calibration database.

As the delta_max has been fixed to 0.7 degrees, the King profile PSF now returns 0 for delta angles larger than 0.7 deg. Furthermore, the PSF is normalized so that the integral from 0 to 0.7 deg gives 1. In that way we assure that the PSF integral is always 1.

The GCTAResponse::load_psf method now automatically detected the King profile PSF. Also, the load method now allow specification of a FITS file as the IRF name.

GMWLDatum
  energy_err(), flux(), and flux_err() methods now return const
  references.

GMWLObservation
  filename(), extno() and extname() methods now return const
  references.

GMWLSpectrum
  telescope() and instrument() methods now return const references.

Is now obsolete.

The GCOMPointing class is now obsolete as no GPointing class is required anymore. The pointing can now simply be stored in a GSkyDir object.