Added and updated translations

app/src/main/res/values-de/strings.xml

app/src/main/res/values-lt/strings_preferences.xml

app/src/main/res/values-pt/strings_messages.xml

app/src/main/res/values-sr/strings.xml

app/src/main/res/values-sr/strings_contributors.xml

app/src/main/res/values-sr/strings_defaults.xml

app/src/main/res/values-sr/strings_error.xml

app/src/main/res/values-sr/strings_setup.xml