services/mongooseim: Propagate toplevelConfig.

This wasn't propagated correctly before and now allows us to set
defaults based on things such as toplevelConfig.networking.hostName
within submodules.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
services/mongooseim: Fix evaluation of the manual.

As the attribute set of mkOption is recursive now and the attribute name
to mkModuleEx has the same name ("description"), we now use "desc" for
passing the module description to mkModuleEx.

We could have also used let and remove the recursive modifier, but
"desc" is shorter, so let's go that way :-)

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
services/mongooseim: Create URLs to all XEPs.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>