renamed gpu::cudev  namespace -> cuda::device

cudev is used for new device layer
renamed gpucodec namespace -> cudacodec
removed perf4au test
removed mark_nvidia.py script
removed compatibility headers
renamed gpu* source to cuda* in core module
renamed gpucodec -> cudacodec
renamed gpulegacy -> cudalegacy
renamed gpuarithm -> cudaarithm
renamed gpuwarping -> cudawarping
renamed gpustereo -> cudastereo
renamed gpufilters -> cudafilters
renamed gpuimgproc -> cudaimgproc
renamed gpuoptflow -> cudaoptflow
renamed gpufeatures2d -> cudafeatures2d
renamed gpubgsegm -> cudabgsegm
renmaed gpu module -> cuda
removed gpu module from OPENCV2_BASE_MODULES
replaced gpu->cuda in files names
replaced GPU -> CUDA