re-added initialisation for current vector which prevents double free segfaults when streaming from fixed data in memory
moved SG_REF to a nicer place
removed prints
-removed KernelToCombinedKernel and replaced by a (proper) obtain_from_generic
-some better error messages
-added possibility to init with single features which are then applied to all subkernels (needed by MMD stuff)
some minor updates
mentioned Gaussian blobs generator
added combined kernel selection example
Merge pull request #890 from karlnapf/master

new example for kernel selection on combined kernels