Docker images for CCF

app_run: Builds the image containing all runtime dependencies for CCF, as well as the latest release of CCF (as per https://github.com/microsoft/CCF/releases/latest). To be used by CCF operators.
app_dev: Builds the image containing all build dependencies for CCF applications. To be used by CCF application developers.
ccf_ci: Builds the image containing all build dependencies for CCF itself. To be used by CCF contributors. It is also used by CCF Continuous Integration pipeline.
ccf_ci_built: Builds the image containing all build dependencies for CCF itself as well as CCF source and a build. To be used by CCF contributors. It is also used by CCF Continuous Integration pipeline.

To build a given image, run:

$ cd CCF/
$ docker build -t <tag> -f docker/<app_run|app_dev|ccf_ci> --build-arg="target=<sgx|snp|virtual>" .