Zend\Escaper integration into Zend\View (BC break since Escape helper is now EscapeHtml)

[padraic]

Integrates Zend\Escaper across Zend\View helpers. Replaces Escape helper with EscapeHtml, EscapeHtmlAttr, EscapeJs, EscapeCSS and EscapeUrl helpers instead. Tests checked for Zend\View and Zend\Escaper.

Other background:

1. 2nd parameter to __invoke() on Escape* classes has been preserved.
2. Rationale for Escape helper deprecation is to enforce selection of correct Escape* helper per agreed RFC.
3. A Placeholder class had an inconsistent use of htmlspecialchars() directly (not via Escape helper). This was replaced with an instance of Zend\Escaper\Escaper.
4. Helpers can likely be refactored a bit further into the Helper\Escaper\AbstractHelper class.
5. Helpers likely still need a brief security review (there's a usage of Zend\Json instead of a true Javascript escaper but is likely safe - will review post-beta).

[travisbot]

This pull request fails (merged 39140db into f8e8120).

[Ocramius]

I'd use byRef here to just remove $k

[Ocramius]

The logic of the AbstractHelper is very very similar to the one of its concrete implementations. You could just reduce the concrete implementations to the simple implementation of

public function doEscape($string);

That should reduce code introduced by this PR by a lot

[adamlundrigan]

Class is named incorrectly (EscapeCss instead of EscapeUrl)