Add i18n for applications in administration

[f1sh1918]

Is your feature request related to a problem? Please describe.
As a dev i want to use a i18n library instead of hardcoding labels. This feature is also needed to resolve application data labels

Describe the solution you'd like

• implement i18n library
• create a translation file for keys and values for german
• replace hardcoded labels by i18n keys for applications

Note: For now we need the i18n for the verein360 interface, since they don't deliver all the application data labels. So we have to resolve them by the keys to be able to show incoming applications to the service users with the correct labels. In general we want to replace all labels by i18n keys but it doesn't have to be done in one ticket