Upgrade to Cuda 7.5 final

[ogrisel]

It's mostly a matter of:

• changing the URL of the cuda installer in scripts/ubuntu-14.04-cuda-7.0.sh (which should be renamed to scripts/install-cuda-on-ubuntu.sh once and for all),
• re-running the 2 scripts (from the scripts/ folder) on a vanilla Ubuntu 14.04 image (changing the default image size from 8GB to 10GB)
• check that everything works
• snapshoting the image an turning it into a public AMI (optional)