Prevented exception when replicating all documents.
Fixed wrong replicant link if target is external.
Removed global JQXHR that was used for debugging or something..
Prefixed target with 'http://' if replication was unsuccessful.

I wouldn't feel so well if the target was prefixed on solely the condition that
it contains a slash and it has no http or https at the beginning, because it
still may constitute a valid local target on CouchBase or some other
implementation.
So I've let one replication deliberately run with the specified target, and
only if this one failed and the above conditions are met, prefix the target and
post replication again.
As a side note, it is a nice gesture of jQuery to apply the callback to the
ajaxOptions object. It makes my day.