Include steemconnect v2 to beem

steem
* add steemconnect in init, when set, steemconnect is used for broadasting
steemconnect
* new class can be used to broadcast operation with steemconnect v2
storage
* Token class to store encrypted token
Transactionbuilder
* use steemconnect broadcast with set in steem
Wallet
* add token storage class
* add setToken, clear_local_token, encrypt_token, decrypt_token, addToken, getTokenForAccountName, removeTokenFromPublicName, getPublicNames
Example
* Add login app for testing steemconnect