libnv: bump library version

Now that we version symbols we should bump the library major version.
While here use version FBSD_1.7 to match the current HEAD FreeBSD
namespace and remove extraneous 'All rights reserved' and incorrect
copyright statement.

Reviewed by: kevans
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D35875