WIP: Bug/open wallet in same browser

Please, DO NOT merge.

This PR:

* Check if you already have opened a wallet in the same browser
* Catch error messages when open or join wallet

TODO:
 
* Create a storage model: LocalPlain.js (handle localstorage without encrypt).
* Make a test for LocalPlain.js
* Replace checkLocked() with new LocalPlain models.
* Fix test.