add gov/types

[tbruyelle]

• copy cosmos-sdk gov/types to x/gov
• rename imports
• rename amino and proto path
• copy cosmos-sdk proto/cosmos/gov in proto/atomone/gov, rename imports and package, regenerate *.pb.go files
• add wrapper for legacy proposal handlers (like in govgen)
• add upgrade and param module client for proposal tx (like in govgen)
• add proposal type registration (required currently executed in related module on the legacy gov module)
• add module types registration where modules used to do it for the legacy gov module