Factorized duplicated code

Better variable naming, and small optimization.

Unclutter graphics package scope.
Moved some import statements from "graphics" package to "viewer" module.
It also avoid systematic import of everything in graphics when we only need one submodule.

Removed dead code

Fixed pyro timeout for runtime, was set too short and runtime was disconnecting when building PLC

Ask to stop PLC before transfer if it is running

Factorized some repeated refresh code into a method, to allow customisation.

Launcher : add a debug attribute, instead of BMZ_DBG, so that customization can use it.

Stripped old dead code.

More changes in Launcher. Modules to be loaded in the background are given in a list, and assigned as object attributes. Also splitted CreateUI into CloseSplashScreen and CreatueUI.

ClassImporter now accepts string, callable or class, for compatibility with some old extensions.

Launcher: ShowUI call moves from preStart to start. ShowUI() split into CreateUI() and ShowUI(). Start()'s arguments are passed to CreateUI()
This is meant to allow customizations to pass own pre-instanciated controller to UI at startup.

Launcher: allows customizations to specify what globals passed to extensions

Documentation

Another set of meaningless changes to satisfy PEP8 and PyLint.

PEP8 conformity for modbus. Most of it done by autopep8, plus some easy refactoring.