Feature request: Add option to set a namespace prefix to ignore

[fbjerggaard]

I have a use case where I use a loader that loads multiple translation files for each module (specifically https://github.com/larscom/ngx-translate-module-loader)

This generates a namespace for each translation file like the following:

ADMIN.MENU.TITLE

The translation file should then only contain the MENU.TITLE part since ADMIN is automatically prefixed