Only Support 1 Address at the Merchant

[StuartFerguson]

This will require changes to the aggregate and also the repository/database.

[StuartFerguson]

Had a think over this a bit more and decided that multiple addresses will be supported as well as contacts but an address type will be available (main, billing, statement).

Contacts will also be enhanced to have a priority option

[StuartFerguson]

Moved this off the sprint as is a larger all round change that needs thought through