add func file_size + del unused func

tools/db/import-md5-list

@@ -142,15 +142,12 @@ function db_query() {
   echo $@ | mysql $args
 }
 
-# db_exist_md5 <md5> -> true/false  0/1
-function db_exist_md5() {
-  result=($(db_query "SELECT COUNT(md5) FROM File WHERE File.MD5 LIKE '$1';"))
-  if [ "${result[2]}" -gt "0" ]; then
-    echo true
-    return $TRUE
+# file_size <path> -> (du -b)/1024  [Kb]
+function file_size() {
+    if [ -f "$1" ]; then
+        echo $(($(du -b "$1" | cut -f 1)/1024))
     else
-    echo false
-    return $FALSE
+        echo 0
     fi
 }