FEATURE: add support for remote node configuration

- any munin-node could support remote or indirect fetching of plugin's data
- add support for munin-node:remote-node syntax of host parameter
- add process logic to ask for remote node data
- displayname should be used to correctly identify such metrics
Merge branch 'indirect-node' of git://github.com/zdenekpizl/munin-graphite into zdenekpizl-indirect-node
cosmetic space between string substitution and variable name