Add logic to notice that the device is offline and notify the
user of this fact on screen.
Repeat checking so we can notify the user that network is back.
This shows in the UI (of the mobile form factor) that the device
is offline and we avoid starting the p2p layer until network
is detected to be there again.
This upgrades us to no longer use the expected block height based
on current time, but instead uses the certainty we get from asking
various peers for their view of the world.
Now when we are certain that we're at the same tip as the rest of
the world, we can safely hide the 'up to date' text and make the UX
again a little bit simpler.
The ImportWalletPage now loads the QML provided by the module,
exposed via the metadata of modules.
The module gets just a blockheight property and then will do
"its thing".
This will either instantly close when there is nothing to do
and continue instantly to the actual import.
Or the module will check the server, initiate download and when
all is setup and done THEN close the popup and continue with
the actual import.
We moved the initial-sync-height from the view to the model, which gives
a more logical progress update when switching between accounts.
Also added a button on the listview to instantly jump to the top of the
list.