handle empty list in wait_for_tasks
refactor wait_for_tasks WIP
refactor wait_for_tasks
destroy property collector after use
updated CLI definitions
Finished release v0.1.2.

* release/v0.1.2:
  updated CLI definitions
  destroy property collector after use
  refactor wait_for_tasks
  refactor wait_for_tasks WIP
  handle empty list in wait_for_tasks