Use Model for storing Pings about erfurt

[seebi]

please use the config ping.modelUri option URL value to define the ping log graph

[white-gecko]

From the mail:

1. Should I add the Pings to "http://localhost/OntoWiki/Config/"
2. Should I add a new graph e.g. "http://localhost/Erfurt/Pings/"

Maybe you should configure 2. for the erfurt default.ini and 1. for the ontowiki default.ini (also 1. can be the hardcoded fallback value)

ac.modelUri is also http://localhost/OntoWiki/Config/ in Erfurt. Either we introduce a new model http://localhost/Erfurt/Config/ or I use 1. for OntoWiki and Erfurt.

Another question:
should I add a method which deletes the old ping SQL table or should I just leave it?

[white-gecko]

I've added the changes to a new branch: https://github.com/AKSW/Erfurt/blob/feature/pingback/library/Erfurt/Ping.php after testing it, I will add a pull request.

[white-gecko]

The pingback in branch https://github.com/AKSW/Erfurt/tree/feature/pingback is read to be merged. Should I sqash it or send all commits?

[white-gecko]

Ok, I've rebased all the stuff and put it into two logical commits