SVGHMI: Add support for forcing widget update frequency with period longer than a second. As an example, "HMI:Display|10s@/myvar" updates variable every 10 seconds.
<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"/>