Fix default value for checkboxes/radios

Reimplement what was done in Phalcon 1.3: https://github.com/phalcon/cphalcon/blob/master/ext/tag.c#L959

Fixes https://github.com/phalcon/cphalcon/issues/3058
metadata default values
HTTP Request:  Adjustments and fixes
[2.0.0] HTTP Request: Fixes and adjustments
Merge pull request #3078 from dugwood/patch-4

[2.0.0] Fix default value for checkboxes/radios
Merge pull request #3134 from brainformatik/2.0.0

[2.0.0] HTTP Request:  Fixes and adjustments
Merge pull request #3113 from quantum13/default_values

[2.0.0] metadata::getDefaultValues