esmero-cantaloupe: add ENV to control XMX and XMS

[DiegoPino]

What the title says. We want to pass ENV arguments to the container so Memory used by JVM can be set (larger production environments).

Also there is a note in Cantaloupe Docs that say

Docker
When running in Docker, consider using JRE 8u191 or later. This version includes support for auto-detecting container CPU and memory settings (see JDK 8u191 Update Release Notes) as an alternative to using VM arguments like -Xmx.

Do we comply? Can we make use of this?