When adding a gas change event via a context menu, the gas-id and
timestamp were passed in two distinct ways.
1) The gas id was extracted from the text of the action. This meant
doing rather complicated parsing.
2) The timestamp was passed via the "user data" of the action, which
means transporting via "QVariant".
There is a much simpler way to pass arbitrary data, that is strongly
typed: lambdas. Instead of shoehorning the data onto the action in
an archaic way, we can simply connect to a stateful lambda. That's
what they're for after all.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
03f9e29146