Include all terms in LICENSE file, add NOTICE

This pull request does not make any licensing changes, but rather includes the applicable licenses for works which DotNetZip is derived from. It also includes the require NOTICE from Apache Commons Compress, as well as other relevant copyright acknowledgments.

This plain-text LICENSE file could be seen as a replacement for /src/License.Combined.rtf. Perhaps the existing .rtf and license files in /src should be removed for clarity; none of them include everything that is required.

[view diff ignoring whitespace](https://github.com/imazen/DotNetZip.Semverd/compare/haf:master...master?w=1).