Add support for LTI Advantage as provider

[ywarnier]

Add support for Chamilo to work as an LTI provider for LTI Advantage.

The current plugin/ims_lti/ folder in Chamilo implements version 1.3 of LTI as a consumer. The goal of this issue is to implement it (probably into the same plugin) as a provider, in a way that will let external systems to create users, record progress and send the results back to an LTI consumer.

Official documentation: https://www.imsglobal.org/activity/learning-tools-interoperability
In particular, the following documents should be useful:

• https://www.imsglobal.org/spec/lti/v1p3/
• https://www.imsglobal.org/spec/lti/v1p3/impl/

We are subscribed to IMSGlobal, so we have access to their validation tools once we have something that works partially.

[ywarnier]

This is already partially implemented, but requires additional efforts to enable specific tools of Chamilo to be shared (at the moment, only a demo game can be shared as an activity provider).

[ywarnier]

Plugin included in 1.11.16 as a "beta" version with support only for the quiz tool