Login functionality

[jo17-dev]

Login and signup functionalities should work

Here is what happens on login:

• take the user's entered password
• retrieve the hash and the salt from db
• generate a hash with the entered password and salt
• compare it with the hash
• if it's, set the user into the "session" attribute
• derive the aes256 key and be ready to unlock datas from db
• redirect user into to the list of his accounts

Here is what happens on signup

• verify if the password is not weak
• verify that the email hasn't already been taken
• generate a salt
• generate a hash with user's password and the salt
• persist salt and hash
• redirect user into the login and his settings