Changes to go along with Swat HTML head entries changes. The layout class now contains its own HTML head entry collection object.
Changes to go along with Swat HTML head entries changes. The layout class
now contains its own HTML head entry collection object.

- The getHtmlHeadEntries() has been removed as the layout should be the top
  level for getting HTML head entries. 
- The displayHtmlHeadEntries() method was removed as we can use
  html_head_entries->display().
- addHtmlHeadEntry() and addHtmlHeadEntrySet() remain so they can be used by
  pages.


svn commit r6285

nburka/site,nburka/site,silverorange/site,silverorange/site