Add support for more complex dialogs

[MatthieuDartiailh]

The idea would be to allow the following kind of dialog definition :
"M{mode}R{range}A{amplitude:+E6}"
The system would automatically query the values of the named properties (only properties should be allowed) and format the response string.
We could store a callable in the _dialogues dictionary and choose how to treat the response depending on whether or not it is a callable.

[safrie]

Five years later, and I would really like this option. Has there been any progress?