first version of gpu::BufferPool for temporary buffers
added GpuMat::Allocator interface
version with Allocator interface
now each BufferAllocator uses own MemoryStack
GpuMat::Allocator now must allocate memory for refcounter too
added posibility to change default allocator for all GpuMat
added multi device support
used several MemoryStacks
fixed compilation without CUDA
fixed test
fixed work with first stack
added posibility to control memory pool usage
fixed test
perf test
temporary disabled async support
fixed async version
simplify memory pool