Komputation v0.7.4

- Created a “cuda” package
- Added a convenience function to initialize CUDA
- Added functions to compile and launch kernels
- Moved the cuBLAS helper functions to a new file within this package
- Added kernels for sigmoid forward and backward propagation
- Implemented and tested a CUDA-based sigmoid layer (for now, the number of blocks and threads has to be specified manually)
- Replaced the CPU sigmoid layer with the CUDA version in the two GPU demos
- Replaced the suffix “Cublas” with “Cuda” in these demos
- Moved CublasOptimizationStrategy to a separate file
- Fixed the name of the forward package in the test sources