Issue #139 - Allow serialization technique used by LoggingInterceptor to be injected

- introduced new interface: ILogValueFormatter
- new base type for value formatters: LogValueFormatterBase
- new formatter type: JsonLogValueFormatter
- updated tests and modules to include the new types
Merge pull request #140 from jbatte47/feature/issue-139

Issue #139 - Allow serialization technique used by LoggingInterceptor to be injected