RStudio : clone and activate RStudio project at startup

[avouacr]

Description of the change

This init script clones a Git repository that contains a RStudio project (*.Rproj) and automatically activates it in RStudio at startup.

Checklist

• [x] I made sure the header of the script describe what the it does
• [x] I precised parameters if needed
• [x] I commented my code where necessary

[fcomte]

I think we should mention in the header that this script take no parameter.