feat: Add more fields incl sender to Parcel

[AlexLamond]

minor:

• Changes the ordering of @property declarations to match the ordering on the Sendcloud API documentation

feat:

• Adds sender_* fields
• Adds collo fields
• Adds Deutsche Post fields
• Adds customs fields (EORI, VAT)

break:

• Replaces requestShipment with request_label as is the format in the Sendcloud API

[casperbakker]

Replaces requestShipment with request_label as is the format in the Sendcloud API

I think there is no need to make this breaking backwards compatibility. It is fine to have a new standard, but can we make the old parameter work as well? That way no code that is in use today would break.