Use URL params to allow import/export of settings

[sithel]

Obviously we can't share the raw files, but it'd be nice if we could share exact imposer settings. Seems like it shouldn't be too hard to slap on a pile of params (and read them at time of loading?) to enable this. There's probably a library out there that makes this extra easy....

Recording idea-- don't think it's a great starter project, but anyone should feel free to tackle it if they'd like. Otherwise I'll get around to it..... eventually....