[AIRFLOW-2779] Add project versions to LICENSE

[ashb]

Make sure you have checked all steps below.

Jira

• https://issues.apache.org/jira/browse/AIRFLOW-2779

Description

• The Incubator PMC requested that we add version information to the
  license declarations to cope with the possibility of projects changing
  licenses on us in the future.

Where possible I have worked out the version we are actually using, but
where that hasn't been possible and the project is still on the same
license (they all were) I have taken the latest version as of right now

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.

Code Quality

• Passes flake8

[ashb]

@bolkedebruin @kaxil @Fokko Could one of you PTAL? I think this is the last thing needed before I can make a v1.10.1 RC1

[Fokko]

Few of the Javascript dependencies are minimal versions. How do we deal with more recent versions?

Eg. https://github.com/apache/incubator-airflow/blob/master/airflow/www_rbac/package.json#L59

[ashb]

Good question. I've been going off this short post on the incubator mailing list:

I checked the source tar with the git tag and the License files.
We need to specify the third party dependencies version as they may have
different License in different version.
Please fix it in next around release.

[Fokko]

Thanks @ashb

I'm fine with merging this one. Maybe drop a follow up question on the mailinglist?