FIX Escape the redirect URL before outputting

Signed-off-by: Stephen Shkardoon <stephen@silverstripe.com>
Fixing FormField not setting readonly attribute on setReadonly(true)
BUG Fix issue with versioned dataobjects being cached between stages
Merge pull request #2983 from tractorcow/pulls/3.0-fix-versioned-partialcache

BUG Fix issue with versioned dataobjects being cached between stages
BUG Fix encoding of JS redirection script
Merge pull request #2987 from tractorcow/pulls/2981

FIX Escape the redirect URL before outputting (alternate implementation)
Cast TreeTitle to HTMLText

Closes #2989
Fix link to the HtmlEditorField API page

Closes #2990
Merge branch '3.0' into 3.1

Conflicts:
	model/Versioned.php
	view/SSTemplateParser.php
	view/SSViewer.php
Correct line length
Merge branch '3.0' into 3.1
Correct errors from differening behaviour between 3.0 and 3.1
Correct line length and indentation
Updated translation masters
3.0.10-rc1 upgrading docs
Merge pull request #2993 from tractorcow/pulls/translation-update

Updated translation masters
Added change log to upgrade docs
Merge remote-tracking branch 'origin/3.0' into 3.1
Fix: WYSIWYG now returns valid HTML in tables

The WYSIWYG by default creates invalid HTML5. Creating a table and running it through W3C validator returns the following error: The border attribute on the table element is obsolete. Use CSS instead.
Add Behat behaviours to click links and submit forms in preview.