numexpr: Define license
tables: Define license
szip: Indentation
szip: Provide meta-data

The license is set to "unfree" as commercial use is not permitted by the
license [1].

[1]: http://www.hdfgroup.org/doc_resource/SZIP/Commercial_szip.html
Merge pull request #3189 from aherrmann/pr_licenses

License meta-data for numexpr, tables, and szip