Add data for 2016 paper onRXJ1713 by HESS about gamma-cat HOT 4 CLOSED

@wegenmat - Some more info what to do:

• Add information to input/sources/tev-000095.yaml following the pattern from input/sources/tev-000001.yaml. Under papers, add 2016arXiv160908671H.
• Make new directory input/papers/2016/2016arXiv160908671H and add files following the example from input/papers//2006/2006A%26A...457..899A: tev-000095.ecsv and tev-000095.yaml

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@cdeil

• added information from RXJ1713 to input/sources/tev-000096.yaml, since this should be the right id refering to https://gammapy.github.io/gamma-cat/sources.html
• commited your suggestions to input/paper/2016/2016arXiv160908671H/tev-000096.yaml
• added some descriptions to 'input/schemas/paper_source_info.schema.yaml'

from gamma-cat.

Note to self: I'm fixing the SED now:
https://github.com/gammapy/gamma-cat/blob/master/input/papers/2016/2016arXiv160908671H/tev-000096.ecsv

The paper gives eflux and eflux_err, and we need to handle this case and compute dnde and dnde_err from that in sed.py.

from gamma-cat.

This dataset should be OK now.

Input files: https://github.com/gammapy/gamma-cat/blob/master/input/papers/2016/2016arXiv160908671H/

Output SED: https://github.com/gammapy/gamma-cat/blob/master/docs/data/sources/000096/gammacat_000096_2016arXiv160908671H_sed.ecsv

from gamma-cat.