Enhance HTML title handling

The default template does allow code to define $title to set the page HTML title, but it’s almost never used by FusionDirectory which always defaults to the «FusionDirectory» title.

We should set the title to «FusionDirectory - $title», with title being the title showed in the header in the connected pages of FusionDirectory.

Login page should be titled as so as well as recovery, forms and invitation page. Setup should also set a title.