Lazy load authcore wallet vault to improve app resume time

[williamchong]

Previous issue: https://github.com/likecoin/likecoin-app/issues/125 Currently when the app resume, we always wait for authcore vault to init, which calls 2 API and costs ~ 2-5 seconds. Authcore suggested that we could lazy init or background init and wallet when resuming app, and only blocks the user when any wallet feature is used