FIX Escape the redirect URL before outputting

Signed-off-by: Stephen Shkardoon <stephen@silverstripe.com>
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)
Fix link to the HtmlEditorField API page

Closes #2990
3.0.10-rc1 upgrading docs
Added change log to upgrade docs