Added new features for backup/restore:
- Added "Backup", "Restore", and "Delete all blog data" buttons
- Backup creates an mdblog-backup.txt file in your home directory
- Restore reads it, and inserts (including duplicates)
- Also added a "Return to List" button when editing a post - but only if it's been saved, otherwise show the save button
- Added styling to links in the article by default - it was definitely very hard to see links in the marked up text without