CSCD-9213: Migration tool updates:
- Performing JTidy only if content isn't a valid XML to avoid contents being changed unnecessarily
- JTidy executed on entire file contents will contain full html and not just contents of body tag
- XPath expressions will return the entire XML structure now instead of just text contents of tags
- Fixed the progress bar so that it reaches 100% now and fixed a potential division by zero when calculating progress
- Link checker will validate cross-site links in format site://SITENAME/path/to/asset
- Files inside of folders are collected as well instead of root level files only
- Fixed an issue with path resolving where leading slash was causing problems
- Added back the root level folder assignments
- Fixed the static value assignments and persisting of both static values and xpaths
- Fixed creation of page's structured data
- More code cleanup