Limit HDFS browser to a predefined list of paths

## Background
The directory structure of HDFS filesystem of a cluster can be very big. It may be hard for users to navigate through the full path every time when configuring a dataset. Also it could be error prone - users could accidentally select a raw folder instead of publish.

## Feature
Make the list of parent paths for 'raw' and 'publish' folders configurable so they could select a folder only in one of these paths.