Extend the rates shortcode for front end shipping calculations

[bobbingwide]

We need to implement the logic to support the optional parameters to the [rates] shortcode.

Parameter	Intended use
zones	Enables you to limit the zones being displayed. Default 'all'
address	Enables you to pre-select the destination
weight	Enables you to pre-select the cart weight
form	Forces the shipping calculator form to be displayed

Possible implementation

weight - pre-selected weight

• An input field to allow the user to specify the cart weight
• An extra column showing the calculated Rate for the matching weights.
• The system will attempt to determine the rates for all the selected zones