add pattern matching to local delivery postcodes

I found a slight problem in the wildcard postcode matching and have implemented an improvement.  I want to deliver to postcodes starting NG2, but I do NOT want to deliver to postcodes starting NG21.  My fix allows postcodes to be specified in the following format:

NG1___, NG10___, NG11___, NG12___, NG2___, NG3___

I hope you find this addition useful.