Allow greater control for xml output and fix bugs with display output

Please consider pulling in the changes in this request. 

1. Home page (root page) now has link generated in sitemap display output
2. Links and Titles correctly generated when nested pages and custom routes are combined.
3. Ability to over-ride content routes with custom routes to set different priority/frequency for output to sitemap.xml.
4. Improved ordering of items output to sitemap.xml (highest priority first).