Generate a use file and put the downloaded sources in the source dir.
Removed medInria-plugins external project, fixed install path to take into account the configration for multi-configuration builders
Add global targets for the independant steps configure, update, build and install
Change the GitHub signature to be purely domain based, otherwise CMake hangs if the IP changes
Enable the update step of subprojects
Merging branch NewOriganisation: sources have been moved outside of build dir