Add hooks to delete users in user-related plugin tables

[ywarnier]

Current behavior / Resultado actual / Résultat actuel

At the moment, when the BigBlueButton conference plugin is enabled and we delete a user that was previously in a meeting, a FOREIGN KEY database error is avoided through this patch: 73c79d2#diff-54a0e60306c5293cc3e5e0579ea80b89R723

Expected behavior / Resultado esperado / Résultat attendu

This prevents the proper, independent, development of a plugin, as each plugin would need its own patch in the core. Instead, use the hook mechanism (already exists for user creation) to make sure the user record is deleted from the plugin table.

Steps to reproduce / Pasos para reproducir / Étapes pour reproduire

Install the BBB plugin
Open a conference
Join with a user you will later delete
As admin, delete the corresponding user
(actually, to reproduce an issue this should be done with any plugin creating a foreign key on the users table)

Chamilo Version / Versión de Chamilo / Version de Chamilo

1.11.4

[AngelFQC]

Currently in BBB plugin has no foreign key from user or other table. 904f6b7

But I sent 2 commits related to this issue.

c51a213 To add a method that will be executed when deleting course (doWhenDeletingCourse), session (doWhenDeletingSession) or user (doWhenDeletingUser). Without the hooks system. But each plugin must implement them when they are creating tables with foreign keys from user, course, and session tables.
2898d5f To implement the new methods in LTI and StudentFollowUp plugins to avoid issues related to foreign keys

[ywarnier]

This seems to have worked for the production portals we tested it on, so I'm approving this (with the special observation that these new functions should be transferred to hooks for 2.0)