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.
<xsd:attribute name="Command" type="xsd:string" use="optional" default="make -C %(buildpath)s all BEREMIZSRC=%(src)s BEREMIZCFLAGS=%(cflags)s MD5=%(md5)s USE_BEREMIZ=1 FROM_BEREMIZ=1"/>