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.
Merge branch '3.2' into develop

Merge the changes that were made for the 3.2.0 release into the develop
branch.
Fix to hide selected reports from ui action menu

Any new reports that were added to the system were also becoming
options in the report action menu in the UI because they had to be
given the purchase.purchase model.  This has been changed to allow this
original behaviour and also allow reports that are of model
purchase.configuration.report that do not get listed in reports action
list in the UI, but can still be associated with orders.
Move configuration to its own form and menu item

So that the report configuration is consistent between the Sale,
Purchase and Stock modules the configuration for the module has been
moved from the Purchase Configuration form onto a form of its own.  A
menu item for this new form has been created under the Purchase /
Configuration menu.

The name of the form and classes that make it up have been made
consistent across the module.
Prepare release 3.4.0

Version number increase and change log update to make the package
ready to be released as version 3.4.0.
Release 3.4.0

Merge release branch 3.4 in to master as release 3.4.0.