crashing on invalid ini file load

Currently the config file loader crashes out with a KeyError if there are parameters in the config file not present in the plugin.
This isn't great. Should generate a warning and a nice pop-up display.

Probably should also be checking for changes in plugin revision and warning about those too.

also, if it is called with a nonexistent .ini file it doesn't load anything but also doesn't show an error, which is confusing.