mutli gauss class, effective area class and irf info script
Added test data for ARF and PSF
ARF and PSF tests
Changed pyfact to use new arf class
Merge pull request #142 from adonath/psf_analytical_class

Add PSF and ARF class and gp-irf-info script
Add gammapy/utils/array.py and fix test error in gammapy/irf
Implemented distributions as astropy models

Conflicts:
	gammapy/astro/population/spatial.py
Changed all models to astropy models added testing and docs
Changed code to use quantities