FR: install the firecloud python library in the R image

[mbookman]

Unless there is a recommended alternative method of accessing the firecloud API from R, please install the firecloud Python library. For R notebooks that access workspace, data, the approach we have used in the past is to use reticulate to call into the Python library.

I can see that the Python Dockerfile includes:

&& pip3 install --ignore-installed firecloud==0.16.25 \

would be great if the R Dockerfile did the same.

Installing reticulate in the R image would be helpful here as well.

[jmthibault79]

#93 adds reticulate