docs: RWD website - upgrading bootswatch theme file

This patch updates to the latest bootstrap versione (3.3.0) and
contextually pushes the colour theme and fonts required by
our style. The patch provides source files (*.less) to
recompile bootstrap.min.css .

Signed-off-by: Angelo Compagnucci <angelo.compagnucci@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>