[#4761] Convert exceptions to warnings

- To retain BC, filters should never raise exceptions
- Instead, raising warning and returning original value
[#4761] Added tests for null values

- null values should be filtered without warnings
[#4761] null values should not raise warnings

- null values should not be filtered, and should not raise warnings
Allow unsetting cookie attibutes by resetting to null
[#4778] Add zend-filter as optional dependency
More consistent interface: Add "return $this" to set*() methods that didn't already have them.
Fix issue where setExpires(0) works, but $expires=0 doesn't work in the constructor. Remove redundant input checking from constrcutor in favor of that offered by the set*() methods.
Make @var docblocs more consistent for cookie attributes. Only one of specified null.
Update Zend_Validate.php

The String "File '%value%' does not exist" was not translated correctly.
Add checks to see if we have a class to instantiate

Also added a special case for when we're mistakenly trying to instantiate an interface
[validator] Validate quoted local part of email addresses

 Test for validate quoted local parts following the RFC 5321
[validator] Validate quoted local part of email addresses

 Fix for the validator issue
Annotate expires may be a string or an int
Add unit tests for changes SetCookie behavior
default mode variables from static:: constants
Fix showdecimals Issue when viewhelper is executed sequentially
create, delete, get, getList and update method shouldn't be abstract in AbstractRestfulController

Since no method is mandatory in REST, AbstractRestfulController shouldn't force to implement these methods (create, delete, get, getList and update) thus conducing to a concrete class with empty/unused methods.
Zend\Authentication\Adapter\Http::_challengeClient() should be public since one could need to call it this way:

<code>$auth->getAdapter()->challengeClient();</code>

for instance when the authenticated user tries to access a resource for which he is not granted by ACLs.
changed _challengeClient() as deprecated proxy
unimplemented http methods set a 405 status