Minor change to invoke make3FGL.xml

[joeastro]

In the Generating_XML_Models thread, the cell/line that reads:

%system make3FGLxml.py -h

Should be changed to:

!python make3FGLxml.py -h

This is because the make3FGLxml.py script is not set with executable permissions.

The next cell, which uses make3FGLxml.py to make a model file, should also be changed (also keeping in mind the absence of a /vagrant directory).

Should also add gll_psc_v16.fit to the top level of the fermi-summer-school repo.

And write the output to the data/ directory, since the user doesn't have write access to the top level of the fermi-summer-school repo.

!python make3FGLxml.py gll_psc_v16.fit data/3C279_mktime.fits
--outputxml data/3C279_model_py.xml
--galfile data/gll_iem_v06.fits
--galname gll_iem_v06
--isofile data/iso_P8R2_SOURCE_V6_v06.txt
--isoname iso_P8R2_SOURCE_V6_v06
--extDir Extended_archive_v15/Templates
--radLim 10 --sigFree 7 -m False

[kialio]

This is @not-kimiko's thread. I'll let her take care of it.