Update project structure and build process

libwallet/errors/errors.go

@@ -0,0 +1,28 @@
+package errors
+
+import (
+	"errors"
+	"fmt"
+)
+
+type Error struct {
+	err  error
+	code int64
+}
+
+func (e *Error) Error() string {
+	return e.err.Error()
+}
+
+func (e *Error) Code() int64 {
+	return e.code
+}
+
+func New(code int64, msg string) error {
+	return &Error{errors.New(msg), code}
+}
+
+func Errorf(code int64, format string, a ...interface{}) error {
+	err := fmt.Errorf(format, a...)
+	return &Error{err, code}
+}