This polishes the wording in the README a bit where it seemed either
convoluted or strange to me. On top of wording it updates the directory
structure to reference gpcontrib, and removes mention of TINC with the
rationale that anyone reading this file is a new contributor and there
is little value in bringing up a framework which is its deathbed. It
also fixes the links to the website to actually work, since they site
redesign broke the old links without redirects. The ORCA naming is
discussed with all mentions changed to GPORCA, since that's the name
used in the documentation.
Reviewed-by: NHeikki Linnakangas <hlinnakangas@pivotal.io>
Discussion: https://github.com/greenplum-db/gpdb/pull/6648