Make FormattedText generic?

[laeubi]

I played around with FormattedText and think it is quite useful to supply users with restricted inputs.

Still it uses generic Object but depending on an actual type internally and throwing all kind of exceptions otherwise.
There is only one feature that benefits from this that seem one can replace a format with something else, but this to me looks of rather limited value and actually makes the code harder to use.

As the widget is marked as ALPHA state I would like to propose rework this by using generics in the first place, I could propose PRs for this if there is agreement on this.

[lcaron]

Hi Christoph

Pretty Good idea ! Feel free to ask if you need help.

Thank you

Laurent