Add location support for LPL

[ackwell]

needed so lpl can set location when loading outside plugin dir.

note from cara:

add

public string Location { get; private set; } = Assembly.GetExecutingAssembly().Location;
private void SetLocation(string path) {
   Location = path
}

and then any time you want to get the plugin directory use Location
LivePluginLoader will call the SetLocation method when loading the plugin