[LEGAL] Use global LICENSE/COPYRIGHT files, remove boilerplate text

- Preserved explicit 3rd-party copyright notices
- Explicit boilerplate should not be necessary - copyright law applies
  automatically in all countries thanks to Berne Convention + WTO rules,
  and a reference to the applicable license is clear enough.

debian/copyright

@@ -3,9 +3,9 @@ Upstream-Contact: Odoo <info@odoo.com>
 
 Files: *
 Copyright: (C) 2004-2015 Odoo SA. (www.odoo.com)
-License: AGPL-3+
+License: LGPL-3+
  This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU Affero General Public License as published by
+ it under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  .
@@ -14,6 +14,6 @@ License: AGPL-3+
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Affero General Public License for more details.
  .
- You should have received a copy of the GNU Affero General Public License
+ You should have received a copy of the GNU Lesser General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
- 
+