Add /privacy logging command

Add ability to completely turn logs off,
Needed since `/logging` and `/history` didn't stop history logging
in the DB, only in files.
Command might break something on usage,
hence it was primarily introduced for privacy geeks.
Privacy command discussion #1836

src/config/preferences.h

@@ -127,6 +127,7 @@ typedef enum {
     PREF_NOTIFY_MENTION_CASE_SENSITIVE,
     PREF_NOTIFY_MENTION_WHOLE_WORD,
     PREF_CHLOG,
+    PREF_DBLOG,
     PREF_GRLOG,
     PREF_AUTOAWAY_CHECK,
     PREF_AUTOAWAY_MODE,