Shapefile rendering feature building efficiency can be improved

Shapefile renderer builds feaetures using the static methods of SimpleFeatureBuidler, meaning there is an unecessary allocation of a attribute array and a SimpleFeatureBuilder object, plus a SPI scan for the default feature factory, at each feature built. This is less than ideal, should be fixed by creating a single, reused SimpleFeatureBuilder out of the feature "loadi and render" loop.