After switching user, there are errors due to requests for previous user's corpora

[arildm]

Corpus ids are saved in browser state, and those corpora are requested as the new user. Until the list-corpora call returns the new list of ids.

Error messages can be improved in #52 but we probably should avoid requesting the wrong corpora at all.

[arildm]

Same if working on one machine/browser, continuing in another and removing a corpus, and then switching back to the first. The state in the first will still contain the deleted corpus.

[arildm]

Store the user id in local store. When handling the jwt response, if the active user is different than the stored id, clear the corpus store.

[arildm]

This also happens when enabling and disabling the admin mode