* Add RStudio default settings for handling history (#79)

Added to Dockerfiles:

- mkdir /home/rstudio/.rstudio/monitored/user-settings

- create file /home/rstudio/.rstudio/monitored/user-settings/user-settings

	- alwaysSaveHistory = FALSE
	- loadRDate         = FALSE
	- saveAction        = FALSE

- chown rstudio /home/rstudio/.rstudio (Must be done else RStudio will not
  load; generates error message).

Originally, this was added to all Dockerfiles in subdir rstudio. However, on
tidyverse builds these settings were overwritten somehow (user-settings file
existed but contents were slim and not equal).

Added similar section to all tidyverse Dockerfiles.

Sample test builds of rstudio and tidyverse images verify settings work as
expected.

* Add RStudio user-settings file

* Modify commit @00bd6da, COPY user-settings to img

Undo changes to RStudio Dockerfiles in commit 00bd6da.

COPY user-settings (commit de308a4) to image on build.

Change ownership of ~/.rstudio directory to rstudio to prevent "Error occured
during the transmission" errors that will prevent RStudio from loading.

See: #79, #80

* Undo tidyverse changes in commit 00bd6da

fixes #77

* Add PAM helper script for Singularity

* Rename auth_singularity.sh to pam-helper.sh, and add to devel image

RStudio Server version in rocker/rstudio is specified as latest version available at default MRAN date of rocker/r-ver.

* Change version of libssl since the older one got archived

* Added update to all 3.4.x versions

* Remove hanging Mac DS store

* Change version of libssl since the older one got archived

* Added update to all 3.4.x versions

pandoc-templates archive 1.18 no longer exists. just get latest version of
pandoc templates instead

switchable Blas implementations for R

remove explicit openblas in R installation, replaced it by the shared Blas system, as used by the debian R package. it is now possible to switch Blas implementation using LD_LIBRARY_PATH or update-alternatives by example. Also added the --with-tcltk flag, that was already automatically setup to make it more explicit.

maintain shiny-server.log logging as per shiny servers default