Add generic BSD 2-Clause license, not hard-coded to FreeBSD Project

The Software::License::FreeBSD.pm module refers to the 2-Clause BSD license, but it hard-codes the FreeBSD Project as owner of the code covered by the license.

This pull request adds a module for a generic 2-Clause BSD license. I assume the existing FreeBSD.pm module shouldn't be changed in case existing users depend on the current, hard-coded language.