Plugin does not remember to use cost/length if chosen

[bipsendk]

If the plugin is configured to use cost/length - then the next time the page is reloaded, it reverts back to using cost/weight.

[derpicknicker1]

This is because of the plugin does not save it in the settings. I think @jasiek missed to add it to the settings.

[foo25amc]

I'm also having this issue. The cost/weight option doesn't seem to calculate cost correctly, so forgetting the cost/length selection renders the plugin useless for me unfortunately.