Convert afb-helpers and app-controller submodules as a shared lib

Close for Guppy

So, I splitted both parts of the afb-helpers library to get the Qt AFB client functions in a dedicated library and make reviews that reflect that change.

However, reviews are almost the same and add the new Qt library in the demo-platform SDK. I did not touch the minimal/core images but calling afb-helpers dependency should not fail the build now.

I got a fix under test and i'll be able to push it in few hours.

Note that https://gerrit.automotivelinux.org/gerrit/#/c/19227/ should be reverted too unless we have a solution quickly. Current builds with -crosssdk fail. See
  https://gerrit.automotivelinux.org/gerrit/#/c/19369/

Hi,

as the Qt5 dependency is a problem, the solution to get rid of it would be to split the libafb-helpers in two distinct libraries. The first would provide the classic afb-helpers functions and the second ONLY the Qt part. Then using a *.inc bitbake file and 2 recipes for both library would solve our problem, then during the migration of projects using the libafb-helpers library, we would have to pay attention on apps using the qt5websocket client's feature to link to the new library and we are done.

OR we workaround the problem using 2 recipes one building the library with qt5 and the other one without. Here we got 2 library with almost the same code excepts the Qt part.

It is a bit a quick and dirty fix, and I think the first solution should be used to be clean and in addition open to the possibility of separate afb-helpers libraries instead of a big one if needed, like now.