PR description

Replace custom written LICENSE file with official text of the license. THIS DOES NOT MODIFY THE LICENSE OF THE PROJECT. The benefit here is in getting GitHub to recognize the license used.

Submitter checklist

Make sure that following is addressed to make the PR easier to process:

• If applicable, changes are covered by either a unit or a functional test.
• If applicable, changes ware verified manually against an OpenStack instance.
• If the change is API related, the PR description links to OpenStack API documentation of that particular endpoint/request (https://docs.openstack.org/api-quick-start/#current-api-versions).
• If the change concerns particular OpenStack service, its name is used as a PR name prefix (ex.: "Neutron: Add floatingIp port forwardings service").
• If the PR closes existing GitHub issue, PR name have prefix: Fix #NNN: .