Add type checks to correctly cast `CNeuronBaseOCL` objects in gradient clipping,
softmax evaluation, and `backProp`/`backPropDfa` loops. Previously, all neurons
were assumed to be `CNeuronBase`, causing invalid pointer casts and incorrect
gradient/output access for OpenCL layers. This ensures proper support for both
CPU and OCL neuron implementations.
- Define MAX_WEIGHT constant (1.0e6) for weight limits in clusters
- Remove redundant barrier from FeedForward kernel (prevents sync issues)
- Port FeedForwardProof and CalcInputGradientProof kernels for max-pooling (no weights, sliding max)
- Port FeedForwardConv kernel for convolution layers (shared weights, multiple output channels)
- Remove unused code and refactor signal condition logic (CSignalPAI)
