Added the possibility to define a default account

Renaming actions in the member tab
Added a BlockchainInspector thread to check for new blocs and refresh the UI

Wont run because we have to port Pynacl code to libnacl

We can export and import accounts

Configuring account reworking
Some bugs fixed

Refactoring
Debugging

Configuring account : changing its name and the communities

Sauvegarde de fichier, utilisation de "factory" pour créer des models a partir de rien ou a partir de json.

Listing des communautés, démarrage du coeur de l'application, avec de le la sauvegarde au format JSON