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
Merge remote-tracking branch 'origin/3.1.0' into 3.1
Removing "Unreleased" text from changelog.
more meaningful error message in ConfigStaticManifest.php (depth < 0)

Changed error from: Fatal error: Hmm - depth calc wrong, hit negatives in /var/www/tangoio.maori.nz/framework/core/manifest/ConfigStaticManifest.php on line 242 

... to .... 


Fatal error: Hmm - depth calc wrong, hit negatives, see: /var/www/mysite.maori.nz/mymodule/code/MyClass.php in /var/www/mysite.maori.nz/framework/core/manifest/ConfigStaticManifest.php on line 240

The first error is completely meaningless and impossible to debug...
Fix test relying on specific member title format.

If a custom member title format was used, the test would fail as it
only expected the default member title format.
API: Add attributes argument for CMSMenuItem.

Currently help menu item is the only external link in the CMS and the ability for it to work is hardcoded in the template. This request makes the target attribute definable by CMSMenu::add_link().

Adds documentation for how to add a basic external link to the CMS.
Merge pull request #2473 from ajshort/pull-1

Fix test relying on specific member title format.