Add titles and decoration to gadgets in the dashboard macro

The macros in a dashboard, acting as gadgets, should have at least titles and wrapper html elements to allow styling (like borders).
There are a few things to implement for this issue:

• add the titles and wrappers
• implement translation of macro names, therefore of gadget titles (see http://xwiki.markmail.org/thread/eq3ysddzyjeq7a4s )
• add support for dashboard specific css, and dashboard-like styles (borders to gadgets, gadget title bar, etc)