Justine Devin / gammalib

# Conflicts:
#	ChangeLog
#	NEWS
#	README
#	inst/cta/src/GCTAEdisp2D.cpp

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

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

Integrate code (default extno and extver handling in GFilename).

The GFilename::default_extname() has been removed and remplaced by an enhanced GFilename::extname() method that either returns the extension name set in the filename, or if not set, the string that has been provided as argument.

The GFilename::default_extname() has been removed and remplaced by an enhanced GFilename::extname() method that either returns the extension name set in the filename, or if not set, the string that has been provided as argument.

The GFilename class handles the decomposition of the filename into the true filename and a FITS extension name.