BUGFIX Versioned_Version->relField() so fields can be used in GridField etc

Copied from DataObject, since we can't use the $fallback opion in this case
(will try to retrieve from wrong class)
BUGFIX: fix for broken layout in insert media dialog - Trac #8232
Fix alignment of selects within GridField filters
Add no results warning to GridField print view.
FIX GridField export and print actions should preserve state.
Docblock and coding conventions for GridField related classes.
FIX: Do not blindly pass input values to GridField_FormAction URL's

The length of input fields can very quickly exceed the max URI length resulting in 414 errors when printing or exporting results.

To access the input values for a specific GridField action, encapsulate this in your own Entwine instance.
ENHANCEMENT Additional image generation functions now self-determine if a modification to the underlying image backend is necessary before generating additional image files.
NEW: Move temp data into a user-specific subfolder, to stop temp-permission bugs from occurring.

Anyone who has run "sudo -u www-data ./framework/sake dev/build" knows that SilverStripe's temp
folder permissions can be very brittle.  This patch resolves this by making the temp folder
user-specific.

To minimise directory pollution it first creates a chmod 777 parent folder with the same name
as the current folder.  It then creates a subfolder of this with the same name as the current
user.

The positive impact of this change is that sake can be used without fear of messing up file
permissions.  This means, among other things, that we can put a Composer post-update-cmd into
the installer to run dev/build.  Progress!

The negative impact is that you will get two caches if you run sake as a different user.  However,
that is much better than the current situation - which is a bunch of bugs - and if you're concerned
about that, you still have the option of running sake as www-data.
FIX: Groups should be able to have titles longer than 50 characters (Fixes: open/5611)
Merge pull request #1334 from wilr/5611

FIX: Groups should be able to have titles longer than 50 characters
Fixed static config access in Currency and i18n (fixes #8341)
Fixed static config in BBCodeParser (fixes #8340)
FIX Clone Config_LRU incl. objects in array

Caused key confusions when using Config::nest()/unnest()
Clarified 3.1 upgrading docs
Merge pull request #1335 from chillu/pulls/config-clone-nest

FIX Clone Config_LRU incl. objects in array
Fixed _config.php references and usage in docs
Config docs improvement: @config and LSB mentions

Also moved some less important "notes" further down the page.
The doc is still written too much like a technical spec, we need
something that's more accessible to beginners.
Fixed Email.admin_email config static naming
Removed unused DataExtension::$extendable_statics

Oversight from cleanup in 876f4c5