* disable in-network updates
* persistent directory for snark downloads
* listen on port 12345 for i2np connections
* restore multi-stage build
* use better ant target
* allow passing -Xmx via the JVM_XMX variable
Many thanks to LoveIsGrief for the suggestions!
ant needed to be updated to >1.9, but the old image used an old alpine
with the max version of ant being 1.8.
The build is split into 2 phases to reduce the size of the image.
A builder makes the installer and installs it in one image.
The installed files are copied over to the actual result image.
