Effects & Events UI cleanup & mobile enhancements.

Modified several screens including the main index page
and the events, effects, and about pages to work better
with mobile devices with widths of <= 480.

This patch uses the viewport and media tags to use
an alternate CSS file for low-width devices.  There are
also some accompanying HTML changes to use classes instead
of hardcoding widths or percentages in the code.  These
classes were added to fpp.css and fpp_480px.css.

Mainly tested using IOS 5.1 on an iPhone 4 in landscape
mode.  It still needs a bit of tweaking to get portrait
mode working properly.  Also tested using Chrome's DevTools
mode to emulate a mobile device.