Normalize and add options for backup, add more file flags options

- Move more function arguments to structs with some convenience
functions.
- Add a flag to enable backup/restore of file flags. It works a little
bit differently depending on system. Since we don't need to do anything
to get file flags on darwin/BSD, it's in the stat buffer so just save it.
For linux we have to open the file and do a
- Add the normalize flag to ReadAttributes. Implementation TBD.
- stub out common xattr file for doc comments

src/duplicacy_xattr_windows.go

@@ -0,0 +1,35 @@
+// Copyright (c) Acrosync LLC. All rights reserved.
+// Free for personal use and commercial trial
+// Commercial use requires per-user licenses available from https://duplicacy.com
+
+package duplicacy
+
+import "os"
+
+func (entry *Entry) readAttributes(fi os.FileInfo, fullPath string, normalize bool) error {
+	return nil
+}
+
+func (entry *Entry) getFileFlags(fileInfo os.FileInfo) bool {
+	return true
+}
+
+func (entry *Entry) readFileFlags(fileInfo os.FileInfo, fullPath string) error {
+	return nil
+}
+
+func (entry *Entry) setAttributesToFile(fullPath string, normalize bool) error {
+	return nil
+}
+
+func (entry *Entry) restoreEarlyDirFlags(fullPath string, mask uint32) error {
+	return nil
+}
+
+func (entry *Entry) restoreEarlyFileFlags(f *os.File, mask uint32) error {
+	return nil
+}
+
+func (entry *Entry) restoreLateFileFlags(fullPath string, fileInfo os.FileInfo, mask uint32) error {
+	return nil
+}