only poll once with --interval 0
add multigraph support
ignore broken plugins that don't return a value at all
Merge branch 'refs/heads/oneshot'
- PEP8 cleaning
- add try/catch exception for most frequent cases
 - catch key_value errors
 - catch socket error for carbon connection
 - catch for multiple exception in multigraph
 - catch exception for hello string read
added update_hostname

* gets the hostname from the the munin connection hello string
* does not override displayname if provided
- use as displayname only hostname not fqdn which could be passwed from hello_string
updated logger message

* the error is not specific to multi_plugin, and can happen with normal plugins
* logging the line that caused this error and the plugin name