[CLA] signature for piemar1

Done at #17817

doc/cla/individual/piemar1.md

+Poland, 2017-06-25
+
+I hereby agree to the terms of the Odoo Individual Contributor License Agreement v1.0.
+
+I declare that I am authorized and able to make this agreement and sign this declaration.
+
+Signed,
+
+Marcin Pieczyński marcin-pieczynski@wp.pl https://github.com/piemar1