Tidy up.
Adds new macro to provide ability to transform from one thrift struct to another.
Adds Macros, Tag and Decode to the api package.

Also changed the decode and tag macros to import their respective constructors.
Changes SplitCustomerCascade example to transform example.

Transform is a superset of split and will, therefore, replace it.
Removes anything related to the Split macro.

It is now superceded by the Transform macro.