Consider Common Type Conversion Service

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

```java
@FunctionalInterface interface Converter{
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.

Start by reviewing the existing converter APIs and implementations in Faces, Persistence, and Rest, then compare their conversion behavior and extension points. Define the scope of the common Converter, registry, context or exception, and ConversionService APIs before identifying compatibility and integration requirements. Done means the shared service and spec-specific adaptation strategy are agreed and documented.

Written by the indexing model from the issue text.