Combine wasmd and wasmgovd into one code package

[ethanfrey]

Summary

It is important to have these two binaries, but it seems heavy to require to copy all code to do so.

Problem Definition

Since the only difference is one configuration option, which is []string{}, we could pass this in from the cli on the build step.

Proposal

Update https://github.com/CosmWasm/wasmd/blob/master/cmd/wasmd/main.go

var EnabledProposals = ""

func getEnabledProposals() []string {
  if len(EnabledProposals) == 0 {
    return []string{}
  }
  return strings.Split(EnabledProposals, ",")
}

Then we set a linker flag in the Makefile, like

-X github.com/CosmWasm/wasmd/cmd/wasmd.EnabledProposals=StoreCode,InstantiateContract

And build two different binaries from the same cmd/wasmd directory, just using a different build flag

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