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.

SVGHMI
======

Contents:

.. toctree::
   :maxdepth: 2

   intro
   syntax
   pages
   clones
   groups
   variables
   configuration
   i18n
   fonts
   hacking
   widgets
   library