vnstat: import from packages, add myself as maintainer

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

net/vnstat/patches/001-conf.patch

@@ -0,0 +1,19 @@
+--- a/cfg/vnstat.conf
++++ b/cfg/vnstat.conf
+@@ -72,13 +72,13 @@ TrafficlessDays 1
+ ##
+ 
+ # how often (in seconds) interface data is updated
+-UpdateInterval 30
++UpdateInterval 60
+ 
+ # how often (in seconds) interface status changes are checked
+-PollInterval 5
++PollInterval 30
+ 
+ # how often (in minutes) data is saved to file
+-SaveInterval 5
++SaveInterval 30
+ 
+ # how often (in minutes) data is saved when all interface are offline
+ OfflineSaveInterval 30