One more patch for Smokeping

Hi!

After a while, new level of Smokeping integration is done. Patch applied to r6340 and r6343 with no problem.

Main results are on the screenshots:

• drawing of coloured graphs from multiple Smokeping servers is available now;
• navigation panel above the graph is filled with the additional functionality.

Other points about this patch are:

• `Average` section is removed as mentioned on the mailing list on Jan 19-th 2015; now tab for each server shows `Aggregate` graph from all servers perspective and `Detailed` Graph per server and this seems to be more than enough to represent Smokeping's data;
• additional, i.e. non-local, Smokeping RRDs are now available not only from Master-Slave mode, which has known implications in the security (no way to use authentication for web interface when Master-Slave is enabled) and manageability (not all Smokeping server may have same view of the Targets), but with mapping/syncing directories from non-local Smokeping servers and specifying them as an array in the config.php (see patch for defaults.inc.php);
• to correctly display the navigation pane, Smokeping's files are moved to html/includes/graphs/ping.

Known issues:

• we still don't have a way of reading ping count from either Smokeping's RRDs, or Smokeping's config; now at least a config option, `$config['smokeping_pings']` is available; in future I would like to propose an SQL table, which could contain such options.

And on more notice - this is just a code, that represents my and some other guys opinion on how Smokeping plugin should look like. This code works and doesn't declare itself to be optimal/perfect/etc., just contribution of my efforts to the community. Thanks!