Handle multiple names (override) in the baseStyle in obtainDecorationStyle

[haensch-mauricio]

Currently we obtain the first defined name, but the style being passed may have multiple names defined, so we would like to get the last one in that case.

qmxgraph/page/utils.js

[prusse-martin]

var stylesheet = graph.stylesheet;
var defaultVertexStyle = stylesheet.getDefaultVertexStyle()
var style = stylesheet.getCellStyle(baseStyle, defaultVertexStyle);
var baseRotation = mxUtils.getValue(style, mxConstants.STYLE_DECORATION_BASE_ROTATION, 90);

But calling stylesheet.getCellStyle looks costly.