GSKY docker image

[edisonguo]

Despite the fact that GSKY ships with fully automated build scripts in terms of ./configure make make install. The build and installation of GSKY dependencies in a fresh environment can still be a daunting task. For end users who want to quickly check out GSKY, they need a docker image like many other open source projects do. For our developers, it would be also beneficial to containerize GSKY for a variety purposes such as automated testing, quick dev environment setup, and easy deployment.

Apart from the technical side that creates the docker image, we also need to be aware that NCI needs to

1. Create an organizational account on docker hub to host GSKY images and made them publicly accessible.
2. Find a location to host sample data for at least a minimum GSKY demo. There are a few ways we can host the sample data
   a. Host the sample data on NCI servers
   The problem with a. is the coordination of the ops team and a few human-involved approval processes.
   b. Use github's LBF facility to track the sample data like other source code files
   The free version only has 1G bandwidth per month, which is too limited.
   c. Create a seed GSKY image bundled with sample data and push this image to docker hub
   The following PR took this approach. A seed GSKY image tagged v0 bundles with the sample data.
   Therefore, all the subsequent image built from the seed image will also have access to the sample
   data.