a registry for encoding/decoding and handle pointer logic in structs

[tobowers]

This isn't really intended to be a complete PR (it's missing tests). I just wanted to have the discussion before doing any unnecessary work.

This adds a registry for encode/decode. It also supports nested structs that use pointers to refer to each other, for example:

type MySubType struct {
  MyField string
}

type MyType struct {
  MySubtype *MySubType
  AnotherField string
}

[atticlabs-ci]

Build triggered. sha1 is original commit.

[atticlabs-ci]

Build started sha1 is original commit.

[atticlabs-ci]

Build finished.