Changed token loading and storing functions

Multiple entries can now be stored in the login json file.
The are stored under the account_type ('github') and username.
If a token already exists under the account_type/username the
token is simply overwritten.

A genterator has also been added to generate all the tokens of
a given account type.
implemented user/accounts menu

The userPushButton show the active account and the menu shows all
other accounts available. When a account is selected from the menu
it become the active one and the list of repos update.