Move dx.dex.code.DalvOps -> dx.io.Opcodes.

This breaks a nascent circular dependency, keeping dx.io the lower layer.

Bonus: While I was in the territory, I clarified the data payload
opcodes, including adding explicit constants for them.

Change-Id: I8655064ebc3b5713cbb4a6c83bcc90984393701f
17 files changed