Dockerfile(s) moved to docker/ subdirectory

When Dockerfile is in the main directory, during docker build whole website content is send to Docker daemon (this is docker build context). It is over 200MB and we really don't want it. .dockerignore at this moment doesn't seem to work ;/
build.sh re-written so it support --preinstall flag

This reflects most recent changes in million12/typo3-neos-abstract base containers, where this script is called with '--preinstall' param. This allows us to install time consuming things during image build process, instead of during container run time.
NewRelic tracking script removed, Pingdom added
Content Sites.xml sync: cosmetic changes