added binary to create bash completion

also do not bail out, when configs can't be read, still the

cmd/bash_completion/bash_completion.go

@@ -0,0 +1,23 @@
+// usage: ./bash_completion <FILE>
+package main
+
+import (
+	"fmt"
+	"os"
+	"github.com/hpcng/warewulf/internal/app/wwctl"
+)
+
+func main() {
+	fh, err := os.Create(os.Args[1])
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	defer fh.Close()
+
+	if err := wwctl.GenBashCompletion(fh); err != nil {
+		fmt.Println(err)
+		return
+	}
+}