- fixed an issue where some undesirable parts of
   the spack source tree were being copied into
   the image context.

 - added a workaround for a tty ioctl warning on
   ubuntu

 - adjusted how the main images are built so that
   `RUN spack ...` works automatically for child
   images that base themselves on them.

* Unite Dockerfiles - add build/run/push scripts
* update docker documentation
* update .travis.yml
* switch to using a preprocessor on Dockerfiles
* skip building docker images on pull requests
* update files with copyright info
* tweak when travis builds for docker files are done