Add the option to define custom renderers for menu items and implement renderers to
display all unhandled services and host in a badge in the navigation.
resolves#7114
Especially on browsers with slow JS like IE8 iterating again and again
over all rows used to harm response rendering. Immagine a dasboard with
a total of a few hundred rows refreshing every 10 seconds while taking
3 secs to render one dashlet... it's far better right now.
refs #6417