[QGIS-Developer] Splitting Docker utils from core repo ?

[Sandro Santilli]

I'm looking at the official qgis/qgis docker images for use
in plugin testing and wondering why such support is part
of the main qgis repository.

Why not, you'd ask ?

Well, I found some issues with the qgis_setup.sh script for
example, and filing an issue against the main qgis repo, which
already has more than 3500 issues pending, sounds like adding
a drop in an ocean.

The issue is that running the qgis_setup.sh script exits with
a success exit code and no text printed to tell me if it did
anything, while it looks to me it didn't do anything...

Other issues are related to the README file in the docker dir,
which seems to be talking about Travis too much, while not
all plugin developers are using Travis to test their plugin.

--strk;