Test suite improvements

[Maks3w]

From the first commit up to Improve PHPDoc types (a6e9b0c) It's basically CS.

To be backported to 2.4 LTS:

• Consolidation of Factory Exception expectations + namespe bug
• [Factory] Fix unsafe call non InputInterface methods
• Consolidation of InputInterface::merge and Fix unsafe merging
• Fix allow_empty / continue_if_empty cases

This PR could be partial merge at least up to the commit Assert objects are instances of the expected type and the three commits from above

PHP < 5.5 Incompatibilties:

• Use of FQDN::class constant instead FQDN string
• Use of yield keyword

[Maks3w]

I've open an issue on zend-validator for make 0 and 0.0 to be non empty https://github.com/zendframework/zend-validator/pull/35

[Maks3w]

I think "required: false" should not be an exclusion for not reject the input if "allow_empty:false"