Improvements to existing code: debug tools & preparation for adding future modules.

* [DATAHUB_DOWNLOAD,SC] Reusing a lot of code from DATAHUB_GENERICS.
* [DATAHUB_GENERICS,SC] Added predicates we want to reuse in future modules, coming from DATAHUB_DOWNLOAD.
* [DATAHUB_INIT,NEW] Added initialization file that mostly loads in modules for debugging purposes.