cmd: creates generateseed command

Main purpose of this is to quickly test wallet builds that require seeds that are external to the wallet's db

cmd/genseed/README.md

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+generateseed returns a cryptographically secure random seed in either mnemonic or its hexadecimal form.

cmd/genseed/generateseed.go

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+package main
+
+import (
+	"encoding/hex"
+	"flag"
+	"fmt"
+	"github.com/decred/dcrwallet/walletseed"
+	"os"
+)
+
+var (
+	s = flag.Bool("mne", false, "Optional command line argument to print as seed as a mnemonic phrase rather then its hexadecimal form")
+	b = flag.Uint("size", 32, "Optional command line argument to print a seed as a certian size.  The default size is 32 and recommended size is between 16 and 64.  Anything under 16 or 64 will cause the program to crash")
+	m = flag.Bool("master", false, "Optional command line argument to print master key of the created seed.")
+)
+
+func main() {
+	flag.Parse()
+
+	sb, err := walletseed.GenerateRandomSeed(*b)
+	if err != nil {
+		fmt.Print(err)
+		os.Exit(1)
+	}
+
+	var seedString string
+	if *s {
+		seedString = walletseed.EncodeMnemonic(sb)
+		fmt.Printf("%v\n", seedString)
+		os.Exit(1)
+	}
+
+	seedString = hex.EncodeToString(sb)
+	fmt.Printf("%v\n", seedString)
+}

cmd/genseed/generateseedtest.sh

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+#!/usr/bin/env bash
+
+# Test 1: generateseed with no options
+SEED=$(./genseed)
+if [[ ${#SEED} -gt 64 || ${#SEED} -lt 16 ]]; then
+    echo "test 1 failed" 
+    exit 1
+fi 
+
+# Test 2: generateseed with option --mne set as true, and --size as 64
+PARAMS=$(echo \
+    "--mne=true" \
+    "--size=64"
+)
+
+SEED2=$(./genseed $PARAMS)
+if [[ $(echo ${#SEED2} | wc -c) -gt 500 ]]; then
+    echo "test 2 failed"
+    exit 1
+fi