Maintain multiple configurations in localStorage

[RubenVerborgh]

Currently, localStorage can only contain one RP configuration, but this configuration is specific to the IDP and the redirect URI. If any of these are different, a new RP is created (which was introduced to fix #54). This potentially creates a lot of RP entries on the server.

[melvincarvalho]

Much needed. I think I've been running into this alot today.

Will create reproducible steps if I can nail them down.

[RubenVerborgh]

@melvincarvalho You will not run into any visible problems anymore after #54. But the consequence of that fix is that many RPs are created under the hood. It will work—it's just not efficient.