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.
Added json navigation view.
javascript cleanup.
tree: insert all DOM nodes at once.

this reduces the repaints required.
add caching for navigation.json
refactor navigation.json to no longer use ftw.treeview.
uninstall ftw.treeview.
make it faaast with locale storage cache.
include og version in tree cache key so that releases flush the cache.
fix current node selection.
fix navigation unit tests, we no longer sort it there.
enable gzip compression for JSON response.
clear browser caches on hard refresh.
change profile version to 400.
update changelog.
Merge pull request #476 from 4teamwork/jin-tree-portlet-2.0

Added json navigation view.