Refactor the wiki to use page aliases instead of the current 'page names'.

• Migrate all existing page names to the aliases table
  
• Re-work links generated for the index and child list to use the alias
  
• Re-work wiki pages to allow for an alias in the url
  
• Re-work the "move page" system to just set the alias and consider how re-directs could potentially work. (When you move a page, just leave the old alias in-tact and clear it's 'preferred' flag.)