Make subimages compatible with late user creation

* Always remain as root during install
* Put kernel specs in system path, not user home
* Create user work directory at startup
* Note this is in 4.0 and up images, not 3.2

Contribution (c) Copyright IBM Corp. 2015

r-notebook/Dockerfile

@@ -11,8 +11,6 @@ RUN apt-get update && \
     gfortran \
     gcc && apt-get clean
 
-USER jovyan
-
 # R packages
 RUN conda config --add channels r
 RUN conda install --yes \
@@ -33,6 +31,3 @@ RUN conda install --yes \
     'r-caret=6.0*' \
     'r-rcurl=1.95*' \
     'r-randomforest=4.6*' && conda clean -yt
-
-# Switch back to root so that supervisord runs under that user
-USER root