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.
from __future__ import absolute_import
from etherlab.etherlab import *
from util.BitmapLibrary import AddBitmapFolder
import util.paths as paths
AddBitmapFolder(os.path.join(paths.AbsDir(__file__), "images"))