client/rest, modules/coin/rest: moved code around

After offline emails and a video call with @ethanfrey,
a goal was decided to move things around i.e:
- [X] Move /build/send and /query/account to modules/coin/rest

Due to that move, there is a lot of overlap between needed
code and utils so extracted common code to make
https://github.com/tendermint/tmlibs/pull/33
so make sure to pull in that commit into your tmlibs tree.

After code review feedback:
client/rest, modules/coin/rest: FoutputProof, PrepareSendTx helper

* Extract OutputProof to FoutputProof helper that can
be used in modules/coin/rest/handlers.go as proofs.FoutputProof
* Revert r.HandleFunc("/tx", doPostTx).Methods("POST") which
was erraneously deleted
* Use function signatures from "tendermint/tmblibs/common"

cmd/baseserver/main.go

@@ -1,12 +1,9 @@
 package main
 
 import (
-	"fmt"
 	"log"
-	"net/http"
 	"os"
 
-	"github.com/gorilla/mux"
 	"github.com/spf13/cobra"
 
 	"github.com/tendermint/basecoin/client/commands"
@@ -20,24 +17,12 @@ var srvCli = &cobra.Command{
 	Long:  `Baseserver presents  a nice (not raw hex) interface to the basecoin blockchain structure.`,
 }
 
-var serveCmd = &cobra.Command{
-	Use:   "serve",
-	Short: "Serve the light REST client for tendermint",
-	Long:  "Access basecoin via REST",
-	RunE:  serve,
-}
-
-var port int
-
 func main() {
 	commands.AddBasicFlags(srvCli)
 
-	flagset := serveCmd.Flags()
-	flagset.IntVar(&port, "port", 8998, "the port to run the server on")
-
 	srvCli.AddCommand(
 		commands.InitCmd,
-		serveCmd,
+		rest.ServeCmd,
 	)
 
 	// TODO: Decide whether to use $HOME/.basecli for compatibility
@@ -47,20 +32,3 @@ func main() {
 		log.Fatal(err)
 	}
 }
-
-const defaultAlgo = "ed25519"
-
-func serve(cmd *cobra.Command, args []string) error {
-	keysManager := rest.DefaultKeysManager()
-	router := mux.NewRouter()
-	ctx := rest.Context{
-		Keys: rest.New(keysManager, defaultAlgo),
-	}
-	if err := ctx.RegisterHandlers(router); err != nil {
-		return err
-	}
-
-	addr := fmt.Sprintf(":%d", port)
-	log.Printf("Serving on %q", addr)
-	return http.ListenAndServe(addr, router)
-}