Rename license file.
Adjust license file to reference BSD-3-clause.

All contributors agreed upon relicensing their contributions to the
BSD-3-clause license (http://opensource.org/licenses/BSD-3-Clause).

See https://github.com/terrestris/shogun/issues/55 for discussion
and the respective agreements.
Add file header with BSD-license to source code.

All contributors agreed upon relicensing their contributions to the
BSD-3-clause license (http://opensource.org/licenses/BSD-3-Clause).

See https://github.com/terrestris/shogun/issues/55 for discussion
and the respective agreements.
Reference BSD-license in pom.xml.

All contributors agreed upon relicensing their contributions to the
BSD-3-clause license (http://opensource.org/licenses/BSD-3-Clause).

See https://github.com/terrestris/shogun/issues/55 for discussion
and the respective agreements.