Added option to replicate selection into another database.

I did exactly this by hand more than once, so it should be available in the map
page. The filename text input duplicates as database name to replicate into.
Also I need an extra button because this one has a different caption.
Excluded replicate button from download callback.
This hides spans for column selection for replication.

Obviously they make no sense because the entire document is replicated no
matter what. Also the replicate button is uncovered and everything is reset
back to normal for xml/geojson.
Added non-special dbs as autocomplete source.

I positioned it on top of the text input because we are on the bottom of the
page already.
Added click handler for replication button.

Documents are from the end of the filter queue plus docs from linked geometries
plus the couchgis design document. create_target writes documents to a new
database if it doesn't exist already.
For now I just dumped the response into console.log.
Triggered either a replicate or download click on enter.

If the replicate option is selected, the enter key redirects to replication,
etc.