fix combox and container lua widget behaviour
Generally speaking, comboboxes & containers now appears more like standard lua tables:
- access to numeric element out-of-bound return
nil - access to children of container by index is working (fix regression from 0edd2f42)
After this changes:
- it is possible to get container (box, stack) element by index
- it is possible to use
forwithpairto list all attributes and children of containers & comboboxes - it is possible to use
forwithiparisto list all children of containers & comboboxes
some examples of what this do: tests.lua.txt