Add ExtendedCall to PLCObject as a replacement of RemoteExec and reflect it in eRPC interface.

ExtendedCall is a generic remote procedure call that runtime code can register to and that IDE extensions can call.
For example a fieldbus extension can use ExtendedCall to browse the fieldbus devices connected to the runtime.

Using Groups (svg:g)
====================


Nesting widgets
---------------

Side effects of optimization
----------------------------

Detachable pages
^^^^^^^^^^^^^^^^

Discardable elements
^^^^^^^^^^^^^^^^^^^^