Add ingest folders with symlink

[spaceymonk]

Hi, I wanted to propose a simple change in ingest script.

Reason behind it: I store my documents in a separate storage and instead of copying files I symlink them to SOURCE_DOCUMENTS folder. It works when I link documents one by one (i.e. giving full path for each file). But I have documents in nested folders and linking directories not work due to followlinks flag defaults to False. Documentation

The PR solves this problem.