* implemented kernel code generation for user supplied transform and rasterize programs (via template kernels and slightly insane string processing)
 * note: user-kernels on the device/opencl side should be fully working now; only things missing are the automatic buffer and kernel parameter handling on the host side, and specifying which user programs to use in some kind of context
 * thanks to c++11 raw string literals: moved template kernel code into the actual .cpp files (transform/rasterize program resp.) -> removed old template kernel files
 * removed kernel compilation of previous transform/rasterize kernels (these aren't necessary any more)
 * added in-place core::find_and_replace