Split sublibraries into pure library wrappers and higher-level wrappers

[maleadt]

At some point, we are going to have to use Clang.jl to keep up with NVIDIA adding more API calls to the libraries. Currently however, our wrappers tend to mix the low-level ccall wrappers and the higher-level wrappers in a single file, making it impossible to "upgrade" the underlying" ccall wrappers.

For example: https://github.com/JuliaGPU/CuArrays.jl/blob/master/src/sparse/wrappers.jl should not contain any ccalls
Instead, for CUBLAS I already did the split into https://github.com/JuliaGPU/CuArrays.jl/blob/master/src/blas/wrappers.jl and https://github.com/JuliaGPU/CuArrays.jl/blob/master/src/blas/libcublas.jl

[maleadt]

This is done.