[IMP] Improved code and make file for demo data.

addons/website/data/website_demo.xml

addons/website/demo/website_homepage_demo.xml

addons/website_event/__openerp__.py

addons/website_event/data/event_demo.xml

addons/website_event/demo/website_event_homepage_demo.xml

addons/website_sale/__openerp__.py

addons/website_sale/demo/website_sale_homepage_demo.xml

addons/website_sale/website_sale_demo.xml