alfred: Retrieve aliases from alfred and integrate batadv-vis.

Extending the visualisation data sources by the new batadv-vis,
which itself base ontop of alfred. Also extending the aliases import
by parsing informations from alfred. The last part is possible
through the preprocessing of data with alfred-json, so we don't
need to process the 'broken' format alfred itself supports.

This patch needs batadv-vis and tcatm/alfred-json in the PATH.
alfred: Mark all nodes from legacy support.
rrd: Only decrease client count for legacy nodes.
alfred: Make the alfred based batadv-vis data source optional.
Merge pull request #14 from sargon/master

alfred: Retrieve aliases from alfred and integrate batadv-vis.