add dispense paid checking script

src/memberdb/has_paid_dispense.sh

+#!/bin/bash
+# script to check if a user has already paid via dispense (or purchased an item in dispense)
+# usage: $0 "$USERNAME" "$DISPENSE_ITEM_ID"
+# prints either a date like "Feb 25 17:25:23" or "None"
+
+LOG=/home/other/coke/cokelog
+USER=$1
+ITEM=$2
+
+PURCHASE=$(grep "for $USER" $LOG | grep ": dispense '" | grep "$ITEM")
+if [ "x$PURCHASE" == "x" ] || [ $(echo $PURCHASE | wc -l) -gt 1 ]; then
+	echo None
+	exit 1
+fi
+
+echo $PURCHASE | cut -c1-15