removed eigen3/viennacl includes from some class headers

for #2460: removed Eigen3/viennacl includes from SGMatrix, SGVector, GPUMatrix and GPUVector. Automatic casting from eigen3 types to shogun types now only works with dynamic size eigen3 matrices

@vigsterkr, @lambday, @karlnapf, @lisitsyn Please take a look
@khalednasr this doesn't work anymore?