First attempt at templating Docker files

Template files are in ./templates subdirectory.
Use makefile to specify per-environment template
settings. 

Fixes:
https://github.com/airstack/core/issues/10

Tried many other ways, but this is a known and 
open docker usability issue. For details, see:
https://github.com/docker/docker/issues/2112
Merge branch 'master' of github.com:airstack/core