API Disable discontinued Google Spellcheck in TinyMCE

Replaced by browser-based spellchecking if available (Chrome, Firefox),
with instructions on how to use PSpell as an alternative.
API Change: Make GridFieldConfig objects decoratable

This change promotes GridFieldConfig objects to first-class Object descendants, making them extendable through the decorator pattern.

Relevant discussion in the dev group: https://groups.google.com/forum/#!topic/silverstripe-dev/Z6tu1k05ZmA
Validate 'archiveDate' user data in Versioned

Not a security issue as such, since the user input is sanitized
before being used in Versioned->augmentSQL(). But it shouldn't
reach the session state either, since that's commonly assumed
to be sanitized data, and it leaves unnecessary room for error.

strtotime() has fairly loose validation rules around dates,
but its a good "first line of defence".
BUGFIX: added <param> tag to ContentNegotiator filtering
Fixes silverstripe/silverstripe-framework#1910: shortcodes not parsed in RSS feeds
$.data() for GridField autocomplete (fixes #2440)
removeRequiredField() limits field (fixes #2165)

Added tests to RequiredFields and fixed bugs that were found

Now you:
1. Can't add the same field name many times
2. Can use append RequiredFields correctly without fear of duplicates

I've also added a Deprecation warning to $useLabels as it's not used
*anywhere* in framework
Merge pull request #2446 from jamesgoodmandia/rss-feed-placeholders

Fixes silverstripe/silverstripe-framework#1910: shortcodes not parsed in...
Revert "Fixes silverstripe/silverstripe-framework#1910: shortcodes not parsed in RSS feeds"

This reverts commit 306281ed44dd0e12a6e88d8fa9e43177123ba684.
Breaks HTMLTextTest
API Escape form validation messages (SS-2013-008)
FIX Auto-escape titles in TreeDropdownField

Related to SS-2013-009. While the default "TreeTitle" was escaped
within the SiteTree->TreeTitle() getter, other properties like SiteTree->Title
weren't escaped. The new logic uses the underlying casting helpers
on the processed objects.
FIX Escape breadcrumbs in SecurityAdmin (SS-2013-007)
Check for jQuery in Behat tests

Identified as one potential cause for flickering tests
on our own Selenium box.
Merge branch '3.1.0' into 3.1
Merge remote-tracking branch 'origin/3.0' into 3.1
Don't link record in GridField form message

This is no longer allows through Form->sessionMessage() to avoid XSS.
Don't link record in GridField form message

This is no longer allows through Form->sessionMessage() to avoid XSS.
Updated translations
Minor changelog fixes
3.0.7 changelog