Provide official docker container image

[comuttun]

Should be on https://hub.docker.com/r/sharedocs/sharedocs/ ?

[comuttun]

Note:

• Container image must be small as possible.
  • The best base image is alpine
  • Only JRE and war package should be included in the container. No sbt, npm, and src.

[comuttun]

@roundrop
#20 will be merged?