* Create user jovyan with UID=1000 in the default users group in the Dockerfile
* Set group ownership of user home and conda to root to avoid 'users' group from host access when mounted
* Set stick bit on both paths so root owns subdirs too
* Change jovyan UID if NB_UID is specified and is not the default 1000
Contribution (c) Copyright IBM Corp. 2015
* Only create jovyan and set perms if user does not exist
* Allow docker host mount for NB_WORK: copy skel files if useradd fails because home dir already exists
Contribution (c) Copyright IBM Corp. 2015
* 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