Docker image

Created by: LoveIsGrief

This PR adds a docker image in order to run MuWire in its own service/container.

An image exists for my repo, but once you create an account on Docker Hub, you'll have official MuWire releases.

The size might be able to be reduced in future releases with a modularized JRE.

TODO:

• Decide how to treat incompletes (by default saved in /muwire/.MuWire/incompletes)
• Default MuWire.properties in docker?
• Docker volume for /incompletes? https://github.com/zlatinb/muwire/pull/33/commits/c910a215f524973ca95f77b05aaba632c2032f06
• Try and find out if defaults can be used for i2p.properties in order to remove i2cp.tcp.port=7654 requirement
• Implemented in https://github.com/zlatinb/muwire/pull/33/commits/65e073b1b952a497c074a773c186c7ab3de92a7d

Closes #32 (closed)