#1019: "Actions: old value kept in instance even when out of range"

This is also a step towards ["Improved actions and services format"](http://wiki.orbeon.com/forms/projects/form-runner-builder/improved-actions-and-services-format):

- FR discards actions implementation generated by older FB versions
- it only keeps the parameters of such actions and substitutes an up to date implementation
- FB discards actions implementations generated by older FB versions when annotating the form so that the source of the form is clean
- the FB action editor only generates action parameters and no longer generates an implementation for actions

What's missing:

- action are still clumsily described with XForms constructs
- services are still fully described with XForms