Elasticsearch does not currently include plugins in their packages, and
hosts them as .zip files from https://artifacts.elastic.co/downloads/.
These can be installed from a mirror by changing the elastichsearch-plugin
call to reference a hosted file URI. However, the plugin removal stage uses
the plugin name, so both name and URI have to be known for the remove and
reinstall plugin tasks in the elasticsearch role to work. This commit changes
the plugin data format to add an optional remote field so that a URI can
be optionally used
Change-Id: I2c366cbeb9912c3aba09ecc5e174baa50de28a1f
7f747d0875