The Sweep feature needs the 'previous' transactions to build the new
transaction.
This shows a progress-report per-transaction as they are downloaded.
Additionally this splits the incoming electron-X reply into lines before
processing.
This separates it into two objects in order to make thead-safety easy
using Qt's signal/slot mechanism.
Additionally this removes magic timeout numbers and simply starts a
timer to check for changes and emit a signal if the status actually
needs updating.
Testing also shows that QML calls the getter a LOT, so I also moved the
broadcastStatus to be buffered and just return that on the call.
This incidentally also simplifies the code, double win.
tomFlowee