Feature: added Contexts and CUDA integration + JaccardWeights preprocessing + 1D Array formats

[AmroAlJundi]

Added support for different architectures using Contexts. For details, check #80.

Changes:

• Expanded library to accept differnt architectures (GPU, IPU, etc.) through Contexts.
• Added a new preprocessing: JaccardWeights.
• Added a new Formats: the 1D Array.
• Added CUDA support.
  • CUDAContext class.
  • Two new formats, CUDACSR and CUDAArray.
  • Added a Jaccard Weights CUDACSR function.
  • Compilation and installation modification to include CUDA in compilation and header-only modes.
  • Changed file structure.
  • Updated readme and getting started page with CUDA compilation details.

A note about installation:

• if the library is in compile-mode, then regardless of whether the user compiles and installs it with CUDA on or off, they will be able to use it with C++ compilers and nvcc .
• On the other hand, in header-only mode, if the library is installed with CUDA on, then the user must use nvcc to compile it. With CUDA off, they can use either. However, they won't have access to the CUDA functionality.