Packing for FedEx OneRate, fix DHL test env

• Added option to set FedEx packaging when using OneRate by @khnbb
• Fixed DHL test endpoint URL

FedEx Freight Codes

• Support for FedEx Freight Codes

CVE-2018-0786 Security Fix

• CVE-2018-0786 Security Fix
• Mark USPS Special Handling - Fragile as Obsolete

DHL Decimals Fixed

• Fixed DHL decimals formatting for non-US cultures.

Thanks @oztrkkaan for the contribution.

FedEx Upgrade to v31

v1.1.6

v1.1.6 FedEx v31

FedEx Negotiated Rates and One Rate

• Added support for FedEx Negotiated Rates
• Added support for FedEx One Rate

USPS Special Services support

• Special service requests can be passed to USPS with USPSProviderConfiguration

First-Class Mail fixes

• Change PoundsAndOunces.Ounces to a decimal.
• Allow First-Class Mail International rates to be returned (both letter and large envelope).

Thanks @creinker for the contribution.

Fixed UPS errors not being returned

• Fixed UPS errors not being returned.

Thank @CooleyCode for contribution.

DHL Payment Account Number

• Added DHLProviderConfiguration class to handle all DHL provider options.
• Added PaymentAccountNumber to DHLProviderConfiguration.
• Added IncludeServices and ExcludeServices to DHLProviderConfiguration.
• Fixed "Instance validation error: 'THIRD_PARTY_BILLING' is not a valid value for SurchargeType." for EU to GB FedEx shipping.