Incorporate 17th Shard sign on

[cmpickle]

Allow users to sign in to 17th shard account and this can be used to save user preferences. For example if they enable spoilers, if they expand or collapse the side panels, which view they were last on, etc. If 17th shard account integration is difficult browser storage could also be used to save these settings.

[jofwu]

I definitely don't see a problem with doing that with cookies, or however else it works through browser storage.

I THINK there's technical challenges (or just roadblocks) with tying it to a 17th Shard account. (even if it's hosted in the 17thshard domain) But I'm not very familiar with those... Maybe @marvin-roesch can comment on that.