Add string for set data warning.

    <!-- Format string describing how much data has been used [CHAR LIMIT=20] -->

    <string name="data_used_template"><xliff:g name="amount" example="1 GB">%1$s</xliff:g> used</string>

    <!-- Label for switch about whether to warn user about usage [CHAR LIMIT=30] -->

    <string name="set_data_warning">Set data warning</string>

    <!-- Label for button to set the amount of data before user is warned about usage [CHAR LIMIT=30] -->

    <string name="data_warning">Data warning</string>