Add support for enum naming conventions

[Antoine Malliarakis]

If using non default naming conventions the result of the generated factory code could be inconsistent with the generated typescript code.

Example of problematic config:

 [...]
generates:
   [...]
    config:
      namingConvention:
        enumValues: keep

This would lead to default initialization of enumerations which would be inconsistent in case they are not pascal cased in their actual name.

[Antoine Malliarakis]

This could be seen as redundant with #13 but it seemed to me that the latter was more referring to a lack of documentation on the convention to use for type names.