Added threading of account loading and blockchain watching so that the UI doesn't freeze anymore

Fixing caching bug with blocks being refreshed only every 5 minutes, even if the blocks changed.

Added the possibility to define a default account

New dialog created : PasswordDialogAsker
Needs to be passed throught the Widgets managing the current account

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

Removed old files

Fixed a bug when an inputs would be removed from available ones even if the transaction is refused
Added icons
Display community nodes again
Save community nodes and load them when acccessing a community object

Signing on the way. There is a bug becuse of ucoin API using keyword "self", and it's conflicting with python self keyword.

We can export and import accounts

Configuring account reworking
Some bugs fixed

Account now has Wallets and Communities
Wallets are now managing the network side of ucoin
A community doesnt depend anymore on a wallet
A wallet knows what community it is part of thanks to currency name

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.