Add LICENSE

[alexisjanvier]

No description provided.

[fzaninotto]

To update that repo, I wipe out the previous files, and replace them by the result of the make build-demo in react-admin.

So next time I'll update the source, the license will go... I suggest you add the LICENSE to the demo example instead, so that it ends here.

[fzaninotto]

My bad, I update the GH pages branch, you PRed against the master branch