Added FilePad demonstration files in demos subfolder

demos/7_filepad/infiles/NOTE

+The third-party EAM potential file `Au-Grochola-JCP05.eam.alloy` by
+
+    G. Grochola, S.P. Russo, and I.K. Snook (2005), "On fitting a gold embedded
+    atom method potential using the force matching method", The Journal of 
+    Chemical Physics, 123(20), 204719. DOI: 10.1063/1.2124667.
+
+has been excluded from this repository. You will find it publically available
+for download at https://www.ctcms.nist.gov/potentials/system/Au/ :
+
+https://www.ctcms.nist.gov/potentials/Download/2005--Grochola-G-Russo-S-P-Snook-I-K--Au/2/Au-Grochola-JCP05.eam.alloy
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