add tensorflow module

[AndreasMadsen]

current issues:

• [x] home directory is NFS, one need to register for a SCRATCH directory. - no fix, but instructions are in readme and the script automatically detects if the SCRATCH directory exists.
• [x] cuDNN module is too old (manual registration and download is required) - cuDNN has been updated
• [x] bazel can't find swig (PR: https://github.com/tensorflow/tensorflow/pull/4983) - new tensorflow release builds swig internally.
• [x] bazel can't find as (issue: https://github.com/bazelbuild/bazel/issues/1713) - .patch file "fixes" this
• [x] HPC drivers too old for CUDA 8.0 - drivers have been updated
• [x] recalibrate wall time estimate