SVGHMI: move declaration of "xmlns" javascript const so that widgets can use it.
This was broken in earlier commit, when changing initial execution order because of implementing websocket reconnect.
<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"/>