Feature/reconnect session

A fork from the peerjs library is added, the oficial library must not be used until the next version - which includes our pull request.

Now the session token is stored with the wallet and reused in every connection. The session token is been cached during 24hs. The token is omitted in the backup process.

Finally, the error message for 'wallet already open in other device' is fixed. It stopped working a few commits ago.

Closes #369 - EPIC