Default CMSMain to Versioned::reading_stage("Stage")

Regression caused by https://github.com/silverstripe/silverstripe-framework/pull/2585
Adding behat test for changing theme of site using CMS dropdown
NEW STEP: Pages editable by and renamed manage page permissions feature file
Merge pull request #904 from srizzling/is/cms/892

Added new step Pages can be editable by
Reload "Settings" form on save (fixes #895)

Regression from 920da0d1202ec403c193a0b282f5379bc415c287
ValidationException support in CMS "Settings" UI
More specific Behat assertion for page editability
use Controller::join_links() for listview links

This fixes incorrect adding of the locale parameter when using translatable :

http://site.com/admin/pages/edit/show?locale=nl_NL/11
Merge pull request #899 from mandrew/3.1

Adding behat test for changing theme of site using CMS dropdown
FIX: Prevent "Add Page" button being stuck 'focussed'
FIX: Prevent AssetAdmin duplicate confirmation for file deletion (fixes silverstripe/silverstripe-framework#2639)
Merge pull request #913 from kinglozzer/assetadmin-delete-confirmation

FIX: Prevent AssetAdmin duplicate confirmation for file deletion (fixes silverstripe/silverstripe-framework#2639)
Updated translations
Merge pull request #912 from kinglozzer/cms-page-add-button-focus

FIX: Prevent "Add Page" button being stuck 'focussed'
Updated translation masters
Fixing test failures because of Translatable and SiteTreeSubsites
Merge pull request #924 from halkyon/modules_illegal_extensions_tests

Fixing test failures because of Translatable and SiteTreeSubsites
Fixing test failures introduced by Translatable and SiteTreeSubsites

Same fix as e93abc6, except it applies to VirtualPageTest.
Merge pull request #926 from halkyon/virtualpage_extensions_fix

Fixing test failures introduced by Translatable and SiteTreeSubsites
Fixing test not auto-following admin/pages/SearchForm

With additional modules like Translatable, this test fails because
a 301 is issued to redirect the admin/pages/SearchForm request to the
correct URL containining a locale in the query string.