Prepare sparsity methods
New test
Introduce training_context
Pass the context to the watcher
Sparsity improvements

Alway compute the global sparsity
Store the global sparsity inside the context
Cleanup
Store the reconstruction error in the context
Cleaning
Clean
Compute local_batch
Implementation of local sparsity for RBM/dyn_RBM
Complete tests
Prepare tests
Implement local sparsity method for CRBM