This updates the Elasticsearch chart to allow for setting the
heap size per node type instead of for all nodes equally. This
also adds the required environment variable to configure whether
a node is an ingest node. This is set to false, as suggested for
elasticsearch versions <= 6.x
This also removes the ES_PLUGINS_INSTALL environment variable as
it is not used for anything in the current charts
Change-Id: I9096774db46dcbcd48b8a5448f0510984bf4108f
031ee3e6af