Sweeper with named outputs

I got excited when I found http://avro.apache.org/docs/1.7.5/api/java/org/apache/avro/mapred/AvroMultipleOutputs.html because this is an answer to our excessive sweeper runs for every portal which sometimes hang the cluster. This change redirects entry to a portal-specific named output which gets written to a `country=${portal}` output subdirectory later. So just a single run is necessary through ETLed dataset to sweep for all portals
t.

The only *caveat* is that I need to write a script to change partitioning schema from `country=${portal}/year=${year}/month=${month}/day=${day}` to `year=${year}/month=${month}/day=${day}/country=${portal}`. But that's manageable.

@ljank @vidma 


Well it's either this or we could make it standard hadoopish like: `"country=" + portal + "/part"`. This decides how generated files will be named. Default prefix is `part` as you probably have seen already and this is custom prefix. I think we should stick with custom/per-portal prefix because it might be easier later to do some data moving for example (`part` files would clash). End result looks like:

```
daily/year=2014/month=10/day=10/country=de/de-r-00000.avro
daily/year=2014/month=10/day=10/country=de/de-r-00001.avro
daily/year=2014/month=10/day=10/country=uk/uk-r-00000.avro
etc..
```