Consider Common Type Conversion Service

[hantsy]

Currently, Faces, Persistence, Rest, etc., have their converters. I would like to provide a base conversion service.

@FunctionalInterface interface Converter<S,T>{
   T convert(S source);
}

// ConveterRegistry
// ConvertConext/ConvertException
// ConversionService 

Register the conversion between string and basic types/primary types/DateTime types.

1. To use the common converters, make these specs(Faces, Rest, etc. ) adapt the common conversion service with their converter APIs.
2. Allow developers to register new converters globally.
3. Allow developers to customize the conversion of the existing converters.
4. Also, allow developers to compose spec-related converters as they were, which have a higher order when executing type conversions.