Rename NDoF to NNodes and style updates

Merge branch 'master' into yohann/cuda-restr-opt

Conflicts:
backends/cuda-reg/ceed-cuda-reg-restriction.c
backends/cuda-shared/ceed-cuda-shared-basis.c

Merge branch 'yohann/cuda-non-tensor' [PR #249]

* yohann/cuda-non-tensor:
ceed-cuda: resolve -Wsign-compare for CUresult (unsigned enum) in CeedError
make style.
namespace cuda backends functi

Merge branch 'yohann/cuda-non-tensor' [PR #249]

* yohann/cuda-non-tensor:
ceed-cuda: resolve -Wsign-compare for CUresult (unsigned enum) in CeedError
make style.
namespace cuda backends functions.
Minor: styling
Add CUDA_LIB_DIR_STUBS for systems that don't have CUDA drivers installed
make style
Remove useless function declaration.
Add a reference non-tensor BasisApply for cuda backends.

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make style.

namespace cuda backends functions.

Minor: styling

Remove dead or unnecessary code.

Remove dead code. Cuda-reg restriction optimization.

Optimization of 3D kernels for cuda-shared backend.

Optimization of 1D kernels for cuda-shared backend.

Optimization of 2D kernels for cuda-shared backend.

Minor bug fix

Optimization of weight kernel and dynamic allocation of shared memory.

- First optimization of weight kernel, kernels are now coalesce but
might not be fully using SMs (need to batch elements per

Optimization of weight kernel and dynamic allocation of shared memory.

- First optimization of weight kernel, kernels are now coalesce but
might not be fully using SMs (need to batch elements per block)
- Switch to dynamic shared memory allocation in order to batch elements
for interpolation and gradient in cuda-shared backend.
- Add GetPreferedMemoryType for cuda-reg and cuda-shared backends.
(Can be removed in the future with delegation of this function)

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Update Ceed Delegate refrencing

Remove useless function declaration.

Add a reference non-tensor BasisApply for cuda backends.

Cuda backend using shared memory (#247)

Add a GPU backend based on Cuda using shared memory.

* Draft of a shared memory backend

* New basis apply passes all tests.

* Add the possibility to

Cuda backend using shared memory (#247)

Add a GPU backend based on Cuda using shared memory.

* Draft of a shared memory backend

* New basis apply passes all tests.

* Add the possibility to treat several elements in one block of threads.

* Fix an error in 2D and 3D gradient.

* Put the cuda-shared backend in its own folder.

* Minor cleaning.

* Replace <ceed-impl.h> with <ceed-backend.h>

* make style

* Add a few CeedChk_Cu

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