SVGHMI: provide request_animate() to Widget authors so that they can register redraw code when events lead to redraw. Widget member animate() is called when it is time to update DOM.
<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"/>