Implement TinCan API + LRS

[ywarnier]

Now TinCan seems to be gaining adoption, it is important we support it in Chamilo.

https://xapi.com/developer-overview/

TinCan requires the implementation or use of a Learning Record Store. However, at the moment, there is no existing convincing Open Source LRS implementation in PHP (I found some in Python). This implies that we would be forcing users to install support for an additional language/framework on their server, which we try to avoid as the Chamilo project.

Implementing LRS seems to be relatively straightforward, so we'll do that in-house as part of Chamilo.

Supporting TinCan will then mostly be a matter of implementing an API and storing data in the LRS, and obtaining data from the LRS to show it in Chamilo reports.

This will also enable the integration of the (now famous) h5p service.

This should be done prior to #2666

[lonesomewalker]

Yannick, you can't imagine how happy i am to read this 👍

Even better that it will be done IN Chamilo!

[ywarnier]

@lonesomewalker I'm going to make you go crazy: I think we should link that to BlockChain, somehow (reference for later: https://medium.com/badge-chain and http://hackeducation.com/2016/04/07/blockchain-education-guide). Maybe that's another task, but maybe not...

[ywarnier]

New important data: there is now a GPLv3 Learning Record Store implementation here: https://github.com/LearningLocker/learninglocker (which already has a M00dle plugin), so the development might be considerably sped up thanks to that.
To be continued...