Mooc inter-xblocks link are not (always) rewritten properly

[dattaz]

Sometime in mooc content there is reference to orther part of mooc (another xblocks for exemple).
We should catch them and redirected to the good page offline.
Same in wiki (for exemple first wiki page of https://www.fun-mooc.fr/courses/course-v1:ulb+44001+session04/info)