SVGHMI: add "unsubscribable" property to widgets in order to generalize what already happens for jump buttons.
In most cases jump buttons do not really subscribe to pointed HMI variable, path is given as a relative page jump path. When widget.unsubscribable is set to true, no subscription is made on page switch, but still offset is updated.
This fixes bug happening on relative jump buttons without "disabled" element where offset did not change on relative page switch.
IEC 61131-3
===========
IEC-61131 is a normative document provided by the standards organization IEC
(International Electrotechnical Commission) and describing a standard for
implementing programmable controllers.
The part 3 of this document (commonly named IEC 61131-3) specifies syntax and
semantics for programming language for programmable controllers. Beremiz
implements all the languages described in this document.
http://www.iec.eu
PLCopen TC6
===========
PLCopen is a vendor- and product-independent worldwide association defining
international standards for various topics related to control programming.
For this purpose, PLCopen has 6 technical committees.
The goal of the sixth committee (TC6) is to define a standard file format,
based on XML, for exchanging programmables controllers programmed using
IEC 61131-3 languages. Beremiz uses this file format for saving the PLC
programs of projects.
http://www.plcopen.org