memcpy, memset support for CUDA Array

Resolve #34 (closed)

TODO

• Contexted (split into !61 (merged))
• Memory
• Memcpy
  • refactoring !58 (merged) into a trait
  • For 3D array using cuMemcpy3D is another issue
  • memset requires memcpy3D
• Memset
  • refactoring !59 (merged) into a trait
  • Because CUDA does not have memset for CUarray, we create a host memory and then memcpy it to array.
    • https://stackoverflow.com/questions/11932171/is-it-possible-to-run-cumemset-on-a-cuarray
• Allocatable