Upgrade pillow to 6.2.0

[fabaff]

Description:

• Changelog: https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst#620-2019-10-01
• Update docstrings
• Addresses also Migrate integrations to use top-level imports #27284

Example entry for configuration.yaml (if applicable):

camera:
  - platform: generic
    name: Bärenplatz
    still_image_url: http://www.baerenplatz.be/assets/images/live.jpg
  - platform: proxy
    entity_id: camera.barenplatz
    max_stream_width: 360
    max_image_width: 720

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the [development checklist][dev-checklist]

If the code communicates with devices, web services, or third-party tools:

• [The manifest file][manifest-docs] has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.