Iftach Sadeh / ctools

…he source model to compute the ARF (#2292)

…ding gammalib GSkyRegions(GFilename) method. Added <parameter name='OnRegion' file='..'/> read in for obs definition xml file. Added query for src and bkg method if not specified in case of input event list or input observation file with 1 observation. For multiple observations given in an obs definition file still every bkg region file has to be specified there.

Implemented reading and using of off regions stored in ds9 region files linked in observation xml file.
A line <parameter name="OffRegions" file="bla.reg"/> in an <observation> element in an observation definition
xml file links an observation to its off regions file.
To enable loading of off regions files use bkgmethod LOAD.

… energy bins per decade.

maximum offset is now a parameter