Implement WebId

[jmvanel]

We can leverage on Play wich makes it easy to do OpenID : https://www.playframework.com/documentation/2.6.x/ScalaOpenID ;
then WebId can be implemented on top of OpenId .

The use case is Solid:
which will require access control, which is another story .
I consider read access control a non priority,
because what the world needs is actually more LOD data, open data about products, services, economy in general, state expenses, politics, etc.