implemented binary dump for testing
tuned _CONV, _WENO and partially _HLLC kernels

Using 3D grid and 2D thread blocks improves performance considerably,
especially for _CONV and _WENO
minor
intermediate stage of xextra kernel tune
optimized xextra kernel
implemented Y kernels
tried fused HLLC_Y variant -> no substaintial improvement
minor
improved fused HLLC_Y
Merge branch 'HLLC_Y_fused' into split-CONV-WENO-HLLC
implemented split kernels