Provide i18nd wrappers in kdeclarative

As QML might combine multiple modules with different cataloges we need
to be able to specify the translation domain explicitly. If there is a
need to use a specific domain for all i18n calls (e.g. in a library
using QML) there is the possibility to set a global translation domain
through KDeclarative. If such a domain is set all i18n calls delegate
to the i18nd variant.

Due to the nature of KDeclarative we cannot mix i18n calls with
different domains. If two modules would require to set the translation
domain it's bound to fail. Thus the recommendation is to use the i18nd
variants in any QML code which is intended to be used as an import.

REVIEW: 118526