SVGHMI: add support for "enable expressions" with arbitrary variable name assignment.

HMI tree paths can be prefixed with a variable name "@name=/MY/HMI/VAR"
Widget declarations can end with a "#" followed by a JS expression that refers to name given to variables.
Widget is disabled if expression's result is false.

Commit includes some more-or-less related generated code refactoring, that should simplify extending widget's variables attributes.

# -*- coding: utf-8 -*-

# See COPYING.Runtime file for copyrights details.


def _(x):
    """No translation"""
    return x


Broken = _("Broken")
Started = _("Started")
Stopped = _("Stopped")
Disconnected = _("Disconnected")
Empty = _("Empty")