results.js results.html: plot appearance improvements

1. create less high plots, so they occupy less screen estate
   on netbooks and other small screen devices;

2. move style from style.css to jquery.jqplot.css: there is
   no need to create more confusion, since the latter css file
   is under git (so, I'm not afraid by future merges);

3. better legend position; also, enable more interesting
   plugins, like cursor tootip and highlighter;

4. commit commented-out code to have logscale axes: this is
   still work in progress and won't be in next release;

5. better solution for when there is no data to plot: provide
   a vector that forces jqplot to create empty charts;

6. better code to select x axis format depending on the
   selected time interval;

7. add the plugin needed by point 4. above.
www: don't mention version number in footer

Avoids bugs, like the version number being old in the italian
translation of Neubot.