Andreas Specovius / gammalib

Removed the optional extname argument from:
- GEbounds
- GEnergies
- GGti
- GNodeArray
- GCTAPointing
- GMWLObservation
- GMWLSpectrum

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

The node array class now derives from the container base class. All typical container methods, such as at(), size(), isempty(), append(), insert(), remove(), reserve() and extend() are now implemented. Unit tests have been added to check the functionnality.

The Python interface now implements the __len__ method on the GContainer class level. This allows to determine container sizes using the len() function. The __len__ method is now obsolete in the derived classes and thus has been removed.

I went over all .hpp to make sure that the GBase.hpp file is properly included, and no supoerfluous other includes remain. I also checked that no ostream and GLog friends are no longer available.

I went over all .i files to make sure that classes are derived from GBase.

…s const, add print() method