[BUG] - Design documents cause insert failures

[dalgibbard]

In a CouchDB Database which has _design documents defined (data restrictions, views etc), when exporting the JSON using ./couchdb-dump, these special document types are appended to the end of the JSON dump.
_bulk_docs can't handle these, so the last split file to be inserted fails for all documents contained within it.

The fix here is to break out all of the _design documents from the exported JSON when we want to restore the data, and handle these first.

NOTE: I have the fix for this already; i'll request a merge in a little while.