Run locality checks for ip6 addresses too
sort of support multiple plugin instances

this lets one do

[plugin:geoip]
path = GeoIP.dat

[plugin:geoipcity]
clone = geoip
path = GeoIPCity.dat

it works in the API but the cli tool and web interface get confused and
show multiple identical entries for the plugin.  This is because
it uses .name from the plugin class, not the instance.

Fixing this will probably involve wrapping the plugins, which may help
other things too
don't load disabled clones
simplify plugin object handling.

remove get_inst. so rather than having two kinds of plugin things:

* plugin modules
* plugin instances

Now there are just

* plugin instances that have not been init()'d
* plugin instances that have been init()'d

so now that the code only has to work with plugin instances things are
simpler.
allow overriding metadata fields for cloned plugins
Merge branch 'multiple_configs'
bump version to 0.2.0