GitLab

* Add a Jenkinsfile to drive a pipeline

* Also tweaks the installation script for Jenkins to be more amenable to
running other variants in parallel
* Restrict packaging script to only accept Python 2.7, since I think
that's long been the minimum supported Python version
* Allow run-ctest.py to run tests in parallel (and take advantage of
that in the Jenkins tests).

* CUDA -> CUDA_VERSION

* Jenkins will automatically post result back to GitHub.

Not need to have a separate step do that explicitly.

* Run as a login shell.

* Force looking for CUDA node.

* Make sure we load conda module.

* Start building in a docker slave -- much nicer!

* Try to fix up the installation a little.

* Fix more build issues.

* More build debugging.

* Oops -- recursive :-o

* Put opencl lib in library path

* Try 9.2

* Fix library path

* More updates to Jenkins build recipes.

* Try a new (simpler?) approach with building

* Oops...

clang is tested everywhere else, and it's not as routinely up-to-date on
my Jenkins machine.

PythonInstall failed on Linux machines where the build/install
directories had paths with spaces in them.

- Test system is translated to the origin
- Energy is computed again after updating Gromacs input to reflect no-cutoff option (rcoulomb = rlist = rvdw = 0.0)