Cleanup the postcode selector that was being added multiple times in some cases

See merge request !2

Trigger change and replace deprecated functions

See merge request !1

Update jQuery and trigger change on all billing fields that we touch to trigger other functions (eg. billing address is the same)

Remove accessing $this in static context

Getaddressio alternative to #23

Add functions for postcode validation

Always hide spinner whether or not AJAX call is successful

Add domain setup form

Move settings to admin path

Create new permission to access postcode lookups

Format postcode before searching