This patch set contains the basic framework, a backend plugin for the
FreeOPCUA stack, initial documentation, tests and two examples.

The code is based on initial work by:
Jannis Völker <jannis.voelker@basyskom.com>

Additional work by:
Steffen Imhof <steffen.imhof@basyskom.com>
Sumedha Widyadharma <sumedha.widyadharma@basyskom.com>
Frank Meerkötter <frank.meerkoetter@basyskom.com>

Change-Id: Ia27c67ba5e68bab4485ab14c4bf5f480d815e63e
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>