tox: Remove old comment
window: Remove some old code remainders
Accept requests after changing selection state

Otherwise the check buttons are not removed in time.
tox: New "accept-requests" signal

Use this to be signaled about all accepted request in one go, instead of
using the "number" property of each contact and being notified one by
one.
window: Ensure an active request after accepting

After accepting not all of the existing requests and the active request
was among the accepted ones, the right pane kept showing the info for
the last active request, because we didn't make sure to activate one of
the remaining ones.