Fix lack of import dir accessibility

[drosofff]

@erasche this is a follow up to our conversation in https://github.com/erasche/docker-rstudio-notebook/issues/24

I found a turn around that imply a minimum code change

basically

• the rstudio.ini.sample file should contain use_volumes = False. This is to reflect the abandon of the VOLUME statement in the Docker file

• The docker image should be rebuilt with RUN chmod -R 777 /import/ /home/rstudio && ln -s /import /home/rstudio/import in the Dockerfile and setwd("import") in the Rprofile.site file.

Thus, the ie user finds an Rstudio interface that is not super pretty (with still contains this useless kinematic folder and shows a closed import folder), but apart that, it is workable for a reasonably skilled R user.

Let me know your thoughts

[hexylena]

Hey @drosofff this looks great! Thanks for submitting this patch. Let's merge it.