Merge branch 'develop' into 3.2

Merge the security fix that adds model access rules into the release
branch.
Prepare release 3.2.1

Version number increase and change log update to make the package
ready to be released as version 3.2.1.
Merge branch '3.2' into develop

Merge the changes that were made for the 3.2.1 release into the develop
branch.
Update to ensure conformity with coding guidelines

The python files were changed to ensure conformity to the Tryton
coding guidelines outlined in the document at
https://code.google.com/p/tryton/wiki/CodingGuidelines

The files were checked using pep8 with ignore=E123,E124,E126,E128
as recommended.