Generate release notes that list what changes in all the packages

[tpoisot]

(from a chat with @gabrieldansereau)

It would be cool to list the changes by package -- this can be done with a git log -- from each folder and listing the differences between versions, though it would be cool to automate it for the website.

Moving to the new commit semantic following #177 would help with this too (if we want to separate the commits by type of change)