templated (header + body) approach for building Dockerfile.local + Dockerfile.official w/common guts

Goals:

• "generate" a Dockerfile.official at release time that will satisfy the process/tooling of docker-library for 'official' docker images
  • use a templated approach to fill in things like version, sha512, and GPG fingerprint
• ensure that the generated Dockerfile.official and the Dockerfile.local included in solr.tgz are identical in terms of the "operational" aspects of a Solr docker image (ie: what the disk layout looks like, and how it runs)
  • they should only differ in how they get the contents of a solr.tgz into the docker image (and how much they trust it before unpacking it)
• minimize the amount of overhead needed to make changes that exist in in both dockerfiles