Add support for raw error type

[repli2dev]

Add raw error type into MappingFailedException so it on error mapping (to API or display to form) it can be localized. For now it matches names of the named constructors in MappingFailedException.

[repli2dev]

Simple idea here is pass the __METHOD__ from the named constructors inside instances. Alternatively to use enum if that would be seen as a better option.

[repli2dev]

... I can also prepare PL for this yet here it needs more discussion about the how before I start.