Helper and Inheritance Deprecations

[gsteel]

Q	A
BC Break	no
New Feature	yes
QA	yes

Description

• Json Helper: Deprecate inheritance tree, deprecate setResponse() so it's effectively just json_encode() (Eventually) - The response really shouldn't be modified in the view should it?
• HtmlAttributes Helper: Deprecate inheritance tree - it only needs an escaper to do its job
• The HTML List helper - also only needs access to an escaper
• The Gravatar helper is deprecated completely with all its setters and getters. An alternative implementation is provided that simply returns an tag based on its arguments Moved to Deprecates and replaces the Gravatar helper with a simplified version… #147
• The view model helper doesn't need its current inheritance tree
• The layout helper only needs access to the view model helper so it is changed to pave the way for factory based constructor injection of the dependent helper

There's no need IMO to have this block a 2.20 release

[Ocramius]

Let's split this up: gravatar added in smells a bit 😁

[Ocramius]

LGTM, thanks @gsteel!

Few notes of things that may be improved in future:

• when checking against Foo|null, instead of ! $foo, $foo === null is a better approach, as it will be picked up by static analysis, if the type changes
• when casting object to string, use $object->__toString() rather than (string) $object, which avoids having regressions when $object (by accident) is no longer an object