[#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
[#4778] Add zend-filter as optional dependency
Add info in docblock about warnings

- Added a paragraph indicating inability to filter non-scalar values,
  and that a warning will be raised in such circumstances.
- Updated return annotations to indicate a "mixed" possibility.
Merge branch 'hotfix/4778' of https://github.com/weierophinney/zf2 into pr4778
Merge branch 'pr4778'
Close #4778
`fault` property must be an instance of \Zend\XmlRpc\Fault
Merge pull request #4761
Merge pull request #4761 in master
Removed category, package and subpackage docblock tags
Update Bcrypt.php

Fixed typo in exception message.
update tests/ZendTest/Mvc/ApplicationTest.php
Update BcryptTest.php

Fixed typo in exception message.
Use MvcTranslator, when available, to inject helpers

- Use the MvcTranslator service, when available, to inject view helpers.
Merge pull request #4857 from dimadietto/master

`fault` property must be an instance of \Zend\XmlRpc\Fault
Merge branch 'hotfix/4857'

Close #4857
Merge pull request #4858 from mvargeson/hotfix/2.2

Removed @category, @package and @subpackage docblock tags in ZendTest\Config
Merge branch 'hotfix/4858'

Close #4858
moved description of "virtual" methods up into the class doc block so IDE's can autocomplete for them