LOGSTASH-1201 - Java7/NIO.2 File Input Plugin

Hastily written, barely tested, apparently working.

Submitted for your review & comment.  Any feedback would be appreciated.

I expect it will need a feature or two added before it's ready to merge.  Primarily a sincedb-like way of remembering last position in a file.

Thanks!!!

https://logstash.jira.com/browse/LOGSTASH-1201