net-analyzer/nload: migrate to EAPI=7, shorten description

net-analyzer/nload: migrate to EAPI=7, shorten description

Add -r1 ebuild to fix the following repoman warnings:
"""
  DESCRIPTION.toolong           1
   net-analyzer/nload/nload-0.7.4.ebuild: DESCRIPTION is 83 characters (max 80)
  repo.eapi-deprecated          1
   net-analyzer/nload/nload-0.7.4.ebuild: 5
"""

The description string is suggested by @jonasstein.

Correct the package license in the ebuild as pointed out by @mgorny.
The source code says:
"""
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
"""

Link: https://github.com/gentoo/gentoo/pull/9543#discussion_r209724049
Link: https://github.com/gentoo/gentoo/pull/9543#discussion_r212440187
Package-Manager: Portage-2.3.40, Repoman-2.3.9