FIX Requirement documentation of MySQL driver

Currently the documentation states that the `mysql` module for PHP is required, however as of #84 (over 2 years ago) this is no longer the case and the required module is now `mysqli`.
Merge pull request #2848 from nedmas/patch-2

Requirement documentation of MySQL driver
FIX: Searchable fields with dot notation can be inherited from summary_fields (fixes #1429)
API Removed auto-detection for i18n date/time formats

Default to "yyyy-MM-dd" for date format, and "H:mm" for time_format.
Switched to config API for setting/getting values.

Avoid using "MMM" in particular, since it causes
inconsistencies in month names between jQuery UI and Zend_Locale_Format.

Fixes https://github.com/silverstripe/silverstripe-cms/issues/544
Fixed Filesystem class capitalization
Updated master language file
BUG: Director::test() don't respect port settings in $_FILE_TO_URL_MAPPING

Director::test() don't set the HTTP_HOST with the port number if that has been set.
Later call to Director::makeRelative() will return wrong value because of the strict string matching
(http://localhost/ != http://localhost:8000)

This bug affects all modules that are using Director::test in CLI where the $_FILE_TO_URL_MAPPING
have been set to use a domain with a port in it, i.e. static publishers.
Merge pull request #2852 from stojg/director-test-http-port

BUG: Director::test() don't respect port settings in $_FILE_TO_URL_MAPPING
Merge pull request #2841 from chillu/pulls/dateformat-simplified

API Default to "yyyy-MM-dd" for date format
Merge pull request #2845 from kinglozzer/1429-summary-searchable-fields

FIX: searchable_fields inheritance from summary_fields includes methods called on fields (fixes #1429)
Preliminary 3.1.3 changelog
Updated translations
NEW Allow specifying element whitelist in HTMLText fields
Merge pull request #2853 from hafriedlander/feature/htmltext_whitelist

NEW Allow specifying element whitelist in HTMLText fields
Note about SiteTree.ExtraMeta in security docs
Merge remote-tracking branch 'origin/3.1'
FIX: Fixed regression in ContentController template selection.

https://github.com/silverstripe/silverstripe-cms/commit/47582b3e3c7cad2957087d50b368fddedeeccdfe improved
template selection, but has introduced a regression.  Specifically, it applies to contorllers that are
created by making a direct subclass of Page_Controller (a pattern used in a few modules to make a page
that looks like a CMS page but doesn't appear in the sitetree).  Previously Page.ss would be used as a
template, because when Page_Controller was interrogated in the template stack, the strtok(Page_Controller,_)
was called before looking up the template.

The code was refactored to use SSViewer::get_templates_by_class(), which doesn't do this.  This function
is used by LeftAndMain as well, so rather than re-add the strtok() call, which might cause unintended
side-effects, I've instead just have it ignore _controller in a classname.  Strictly speaking, this is
an API change, but as long as people have followed page type class naming conventions, it will still
work in the relevant cases.
Merge pull request #2881 from sminnee/fix-forum-templates

FIX: Fixed regression in ContentController template selection.
Removing broken reference to "getNextID()"

It doesn't exist.
Merge pull request #2888 from willmorgan/patch-2

Removing broken reference to "getNextID()"