Remove gp_df utility
Remove gp_df utility

This is a OS agnostic df utility that worked on both Solaris and Linux.
However, we no longer support solaris and this isn't referenced or
mentioned in the docs anywhere.

Authored-by: Chris Hajas <e8e414b713ceee89684f46616039fe9bed26bfcc@pivotal.io>

jmcatamney/gpdb,xinzweb/gpdb,50wu/gpdb,lisakowen/gpdb,lisakowen/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,adam8157/gpdb,lisakowen/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,adam8157/gpdb,xinzweb/gpdb,adam8157/gpdb,ashwinstar/gpdb,adam8157/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,xinzweb/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,greenplum-db/gpdb,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,xinzweb/gpdb,50wu/gpdb,ashwinstar/gpdb