Release 6.20.0: Added Latvian translations for standard mail folder names

[changerequest]

The configuration file /opt/open-xchange/etc/admindaemon/User.properties will be extended with the following lines:

# Latvian

SENT_MAILFOLDER_LV_LV=Nos\u016Bt\u012Bt\u0101s vien\u012Bbas
TRASH_MAILFOLDER_LV_LV=Atkritumi
DRAFTS_MAILFOLDER_LV_LV=Melnraksti
SPAM_MAILFOLDER_LV_LV=M\u0113stules
CONFIRMED_SPAM_MAILFOLDER_LV_LV=Apstiprin\u0101ta mu0113stule
CONFIRMED_HAM_MAILFOLDER_LV_LV=Apstiprin\u0101ts ham