Add path configuration file

This file is used by all scripts to find the directories for the files
they read or write. They find this file as "$TOP_DIR/config/paths".

Partial-Bug: 1312764
Implements: blueprint openstack-training-labs
Change-Id: Ia63b8489c66acf174f3b3850d24fd7c6108f59b4
Merge "Add path configuration file"