Add License Permissions, Restrictions, and Limitations

Leverage GitHub License API and/or choosealicense.com to retrieve a list of permissions, restrictions, and limitations for all supported SPDX license IDs.

https://developer.github.com/v3/licenses/#get-an-individual-license
https://github.com/github/choosealicense.com/tree/gh-pages/_licenses

The list of permissions, restrictions, and limitations, should be displayed on the individual license page as well as the license auditing work that will be included in #249.

A ticket was created on the SPDX project to add this metadata to their XML master list.
https://github.com/spdx/license-list-XML/issues/881