Balance details are shown if the user presses and holds the
balance area; the idea is that this should be less chaotic
than if the popup is triggerred by a simple click. However,
we might as well try with a simple click, because we already
do it with transaction details; I am not sure what is the best
option, we should try both.
This also makes 'new channel' and 'swap' buttons available from
theBalance details, so that users do not need to visit the
channels list.
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