Add Apache 2.0 LICENSE file and update copyright headers

[skliper]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I reviewed the CF README.md file to see if the feature is in the major future work.
• I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.
Missing license file and out of date copyright info in file headers

Describe the solution you'd like
Update

Describe alternatives you've considered
None

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC