Minimize required environment variables for setup.py

[PokhodenkoSA]

It is not possible to run stup.py without providing environment variables like:

• DPPL_SYCL_INTERFACE_LIBDIR
• DPPL_SYCL_INTERFACE_INCLDIR
• DPPL_OPENCL_INTERFACE_LIBDIR
• DPPL_OPENCL_INTERFACE_INCLDIR
• OpenCL_LIBDIR

setup.py script should not require all this variables and try to find it from common folders.

[PokhodenkoSA]

Closed by #168