Mail preview tab: fixed bug in mimetype lookup for attachments with a wrong mimetype.
Merge pull request #521 from 4teamwork/pg_mail_mimetypes_lookup_fix

Mail preview tab: fixed bug in mimetype lookup for attachments with a wrong mimetype
Monkey patch ftw.mail.inbound.createMailInContainer because

`preserved_as_paper` has a schema level default, its default
value doesn't get set correctly, so we set explicitely after setting
the defaults.
Merge pull request #524 from 4teamwork/lg-monkey-patch-create-mail-in-container

Monkey patch ftw.mail.inbound.createMailInContainer
Bump version to 3.4.2 and fix changelog after release 3.4.1 from 3.4-stable branch.
Merge pull request #526 from 4teamwork/lg-bump-version-to-3.4.2

Bump version to 3.4.2 and fix changelog after releasing 3.4.1 from 3.4-stable branch.
Referenceprefix manager: Reworked tests and use ftw.testbrowser.
Referenceprefix manager: Removed wrong space in unlock link.
Referenceprefix manager: Fixed KeyError when repository is already removed.
Merge pull request #527 from 4teamwork/pg_referenceprefix_manager_fix

Referenceprefix manager fix, when subitems are already removed.
Add opengever.maintenance to development buildout.
Merge pull request #529 from 4teamwork/lg-add-og-maintenance-to-dev-buildout

Add opengever.maintenance to development buildout.
Pyflakes cleanup.
Include newest theme adjustments for the next release.

Include the fix https://github.com/4teamwork/plonetheme.teamraum/pull/251 which solves #543.
Merge pull request #544 from 4teamwork/pg_icon_for_detailed_view

Include newest theme adjustments for the next release.
Cherrypick from opengever.core release 4.0.

Use correct content-type when returning 'OK' responses.

Conflicts:
	opengever/base/utils.py
	opengever/task/browser/accept/utils.py
Updated the changelog.
Merge pull request #528 from 4teamwork/pg_deadline_modifier_fix

Set content-type correctly for ok_response in inter-client functionalities.
Merge pull request #545 from 4teamwork/pg_pyflakes_cleanup

Pyflakes cleanup
Added json navigation view.