Fix logging bug in run-hooks (order of logging statement)

- The "done running loop" log message was inside the loop, causing it
  to appear over and over again, making log quite confusing.

Updated R packages in datascience-notebook to match r-notebook packages update in PR #786

[ci skip] ARG does not survive past FROM

Hardcode the tag in two places

Add an example binder

Fix bug where container user is "nayvoj"

Addresses code review by @GrahamDumpleton

Updated R packages in r-notebook to match all-spark-notebook update in PR #782

whoami &> /dev/null || STATUS=$? && true
causes STATUS to be set to an empty string
when the container starts with option --add-group="root"
resulting in both nayvoj and jovyan having uid=1000
and gid=100. The first match in /etc/password wins
and so the container user ends up being "nayvoj"
accidentally.

Avoid this by checking that whoami STATUS is neither blank nor 0
before adding a new /etc/passwd entry

fixing inline script problem

Replace vim by nano in the minimal-notebook documentation (fix #779)

Update all R libs in all-spark-notebook for Spark 2.4 

umask flag

Add note about customizing the startup with before-notebook.d

commit 2d92977085983a5936de434f1d646839f2032622
Author: Iyán Méndez Veiga <me@iyanmv.com>
Date:   Tue Aug 21 23:22:35 2018 +0200

    Delete code in start.sh (not necessary). Simplify 'os.umask' code. Add paragraph to docs

commit 19d1e7be71e1eb7632fa8dbf412b8120e55aee03
Author: Iyán Méndez Veiga <me@iyanmv.com>
Date:   Tue Aug 21 19:03:36 2018 +0200

    Change if clause condition

commit 13802f436c36d2d91c36036e2025fd693b4b3bcd
Author: Iyán Méndez Veiga <me@iyanmv.com>
Date:   Tue Aug 21 20:24:38 2018 +0200

    Update jupyterlab & extensions

commit 63bdcad837d79eafecf8548c5ab0b76bd57922c2
Author: Iyán Méndez Veiga <me@iyanmv.com>
Date:   Tue Aug 21 16:21:01 2018 +0200

    Fix 'No newline at end of file'

commit 9504408874e5db286075e9810c9564c0af1a32ef
Author: Iyan Méndez Veiga <iyan.mendezveiga@arcelormittal.com>
Date:   Tue Aug 21 15:37:32 2018 +0200

    Fix if clause start.sh

commit 74da4e07b296e2e568d290a9a660858b8b0e3a2e
Author: Iyan Méndez Veiga <iyan.mendezveiga@arcelormittal.com>
Date:   Tue Aug 21 14:52:21 2018 +0200

    Add NB_UMASK flag to modify default umask

Adding link to a new Community Stack : csharp-notebook

Adding link to a new Community Stack : csharp-notebook is a community Jupyter Docker Stack image. Try C# in Jupyter Notebooks.

Update tensorflow to 1.12

Remove apt-get clean command. Unecessary on official Ubuntu images.