Fixed misnamed USPS services, Added new USPS/UPS services, Removed 'service_name', etc.

Had to rename "Flat-Rate" to "Flat Rate" (as well as one or two other names) in order to match the rates hash returned by USPS.

For reference, this is the rates hash I'm currently getting back for a US address:

```ruby
{"USPS First-Class Mail Postcards"=>28,
 "USPS First-Class Mail Large Postcards"=>44,
 "USPS First-Class Mail Letter"=>64,
 "USPS First-Class Mail Package"=>171,
 "USPS Library Mail"=>229,
 "USPS Media Mail"=>241,
 "USPS Priority Mail Gift Card Flat Rate Envelope"=>495,
 "USPS Priority Mail Small Flat Rate Envelope"=>495,
 "USPS Priority Mail Window Flat Rate Envelope"=>495,
 "USPS Priority Mail Padded Flat Rate Envelope"=>495,
 "USPS Priority Mail Legal Flat Rate Envelope"=>495,
 "USPS Priority Mail Flat Rate Envelope"=>495,
 "USPS Priority Mail Small Flat Rate Box"=>520,
 "USPS Parcel Post"=>530,
 "USPS Priority Mail"=>535,
 "USPS Priority Mail Medium Flat Rate Box"=>1095,
 "USPS Priority Mail Large Flat Rate Box"=>1495,
 "USPS Express Mail Legal Flat Rate Envelope Hold For Pickup"=>1830,
 "USPS Express Mail Legal Flat Rate Envelope"=>1830,
 "USPS Express Mail Flat Rate Envelope"=>1830,
 "USPS Express Mail Flat Rate Envelope Hold For Pickup"=>1830,
 "USPS Express Mail Hold For Pickup"=>2135,
 "USPS Express Mail"=>2135,
 "USPS Express Mail Sunday/Holiday Delivery Flat Rate Envelope"=>3080,
 "USPS Express Mail Sunday/Holiday Delivery Legal Flat Rate Envelope"=>3080,
 "USPS Express Mail Sunday/Holiday Delivery"=>3385}
```

And here is a sample rates hash for an international address (Canada):

```ruby
{"USPS Priority Mail International Small Flat Rate Box"=>1195,
 "USPS Priority Mail International Large Video Flat Rate Box"=>1195,
 "USPS Priority Mail International DVD Flat Rate Box"=>1195,
 "USPS First-Class Mail International Package"=>1476,
 "USPS Priority Mail International"=>2680,
 "USPS Priority Mail International Medium Flat Rate Box"=>2795,
 "USPS Priority Mail International Large Flat Rate Box"=>3550,
 "USPS Express Mail International"=>4345,
 "USPS GXG Envelopes"=>6825}
```

This is the hash I get back from UPS for a Canadian address:

```ruby
{"UPS Express"=>25471,
 "UPS Worldwide Expedited"=>20667,
 "UPS Saver"=>24537,
 "UPS Standard"=>4671}
```

spree_active_shipping didn't have calculators for UPS Standard or UPS Express, and my customer needs them, so I added them.

(Note: I did not add *all* of the USPS services that were missing, but I could if anyone would like...)

I tested all the services I added on our Spree site.

See also:

* https://www.usps.com/send/priority-mail-international-flat.htm
* https://www.usps.com/send/priority-mail-flat.htm?