Syncing screen preventing to do anything else

[Tbaut]

When the node goes out of sync, we are showing a big screen that breaks the user flow (and removes the focus on some field if it happens when typing the password for instance).

As suggested by Amaury we should:

• make this "sync" much less intrusive: what about making the little icon at the bottom left orange and show "Syncing" instead of the green "Sync".
• Only show the "Syncing" state when out of sync for more than 10sec?

[TriplEight]

Sometimes syncing 100% screen appears above any screen and shows, removing the focus from the field.

[axelchalon]

should be fixed with #216 (overlay will only appear in the transaction form/signer and only if the "syncing" takes more than 2 seconds; the focus will still be removed though (and any other info we input, hmm))

[Tbaut]

This is solved now.