[Form] [Type] added widget option

[Form] [Type] added widget option on DateTimeType, DateType and TimeType

"hidden" value will generate separate hidden inputs (day, month,year...) for rendering the formType
"hidden_single_text" value will generate a single hidden input for rendering the formType
On DateTimeType date part can be hidden and not time parts and vice versa

Bug fix: [no]
Feature addition: [yes]
Backwards compatibility break: [no]
Symfony2 tests pass: [no]
Todo: [
- Improve templating integration
- Full Tests and debbuging
]
License of the code: MIT