Improve KuduSync performance in kudu

This change spans 3 repositories:

* kudu - this PR.

* kudusync - a specific branch we're going to use for kudu service that has this extra [commit](https://github.com/projectkudu/KuduSync/commit/3cb29b807ef45dec42a45196f8adfe0752da8a77), with this commit we can use the new fsx_win32 node.js native module described next.

* [fsx_win32](https://github.com/amitapl/fsx_win32) - native node.js module which uses win32 APIs (FindFirstFile/FindNextFile) to get the content of a directory, this allows us to get the directories and files in a directory including a distinction between them and the size and modified time of the files in a single call instead of 1 + n calls where n is the number of files/directories (`fs.readdir` + `fs.stat` per file).

Please review all.