[Resolve #25] Merge changes from #25 into libfabric-sarus branch

[mattnappo]

This PR merges the work started in #25 into the libfabric-sarus branch.

Compile error fixes:
Much of the code that was split into two implementations based on the USE_LIBFABRIC and USE_CRAY_GNI flags were causing errors that did not happen in the libfabric branch. This PR fixes those errors and allows this branch to be compiled.

Core changes:

• JSON configuration of Docker and Sarus containers
• Skeleton code for configuring Singularity containers (initial work on Add support for Singularity containers #12)
• Scripts, rFaaS Dockerfile, and other work from Better, more configurable Docker support #25

[mcopik]

@mattnappo The PR looks pretty good! I have one question only - I want to make a release of rFaaS with ibverbs only and add the container configuration there already. The work with lifabric would go into the next release.

Do you think you could reopen #25 with changes to container configuration based on master, and without lifabric and Sarus?