Silverstripe Forms allow malicious HTML or JavaScript to be inserted
through non-scalar FormField attributes, which allows performing XSS (Cross-Site Scripting)
on some forms built with user input (Request data). This can lead to phishing attempts
to obtain a user's credentials or other sensitive user input.
There is no known attack vector for extracting user-session information or credentials automatically,
it required a user to fall for the phishing attempt.
XSS can also be used to modify the presentation of content in malicious ways.
When constructing a FormField, an IDE would previously tell you the `$title` needs to be string (or null). Let's make it more clear that a ViewableData instance (such as `HTMLValue::create($title)`) is also accepted. This should help people more quickly find a solution to put html in labels.
it's not very likely to happen (it did in my case :-) ) but if the value is an array, sprintf will fail (because raw2att accepts array, but sprintf doesn't). i suggest to json encode any array data to ensure it's safely included in the html. Or we should throw proper exceptions to make sure invalid values do not result in a php error.
Prevent html errors when FormField::create_tag('meta') is called from $MetaTags() so
```
<meta name="generator" content="SilverStripe - http://silverstripe.org"></meta>
```
becomes
```
<meta name="generator" content="SilverStripe - http://silverstripe.org" />
```
Add all void elements to list
API Substitute Zend_Locale with Locale / NumberFormatter
API Substitute Zend_Date with IntlDateFormatter
API Added DBTIme::Nice12, FormatFromSettings
API Added Short() method to DBDate / DBTime / DBDatetime
API Add Date::getTimestamp()
API Added setSubmittedValue api for FormField
API Add second arg to base FormField::setValue()
API Major refactor of i18n into component data parts
API Implement Resettable interface to reset objects between tests
ENHANCEMENT Changed DBField::create_field return type to `static` to support better type hinting
ENHANCEMENT i18nTextCollector supports __CLASS__
