Prepare release 6.0.0 [skip ci]

CHANGELOG

@@ -1,3 +1,5 @@
+Version 6.0.0 - 2021-05-03
+* Bug fixes (see mercurial logs for details)
 * Allow choosing the DPD product and formats
 
 Version 5.8.0 - 2020-11-02

COPYRIGHT

@@ -1,4 +1,4 @@
-Copyright (C) 2016-2020 B2CK.
+Copyright (C) 2016-2021 B2CK.
 Copyright (C) 2016-2017 Nicolas Évrard.
 
 This program is free software: you can redistribute it and/or modify

tryton.cfg

@@ -1,5 +1,5 @@
 [tryton]
-version=5.9.0
+version=6.0.0
 depends:
     ir
     res