Changed meaning of -c commandline argument for Beremiz service : only gives DEFAULT wamp config.
If existing project already has a wamp config, it is taken instead.

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.