Docker integration

[daniele-athome]

• [x] bullet-proof parameter check (i.e. do not even start if something is not right)
• [x] let the user decide if we should use existing PGP keys
• [x] let the user decide if we should use existing X.509 certificate
• [x] use a parameter to choose the branch (master, staging, production)
• [x] HttpUploadComponent
• [x] dev mode: allow auto-generated keys/certificates
• [x] prod mode: must provide keys/certificates
• [x] README
• [ ] db-uri: serverTimezone (escaped)
• [ ] first start shows no Tigase log
• [x] requires GPG private key without passphrase!!
• [ ] bootstrap.sh for asking questions and building the Docker image
• [ ] howto doc (especially for configuration parameters)
• [ ] data volumes
  • [x] public users keyring (kyotocabinet)
  • [x] HttpUploadComponent disk
  • [ ] permissions
• [ ] simple upgradability (i.e. binaries only)
• [ ] database migrations

[daniele-athome]

Moved to kontalk/xmppserver-docker#1.