improved exception handling when finding devices

remove commented code

use to_mem_size instead of duplicating

removed commented code

add reason for commented code

cache retrieval compile_kernel

add OpenCL backend support in print function

add opencl kernel manager tests

add OpenCL to backend enum

comment out tensor functions in manager

remove opencl TensorImpl source from LIB_SOURCES

add opencl backend initialization

Запрос на слияние 'vulkan-batchnorm2d' (#35) из vulkan-batchnorm2d в master

Fix missed backend configuration for BatchNorm tests

Increase accumulator size for Vulkan sum reduction shader

Update BatchNorm tests and fix Vulkan implementation

Use extended accumulator type for CPU sum reduction

add unimplemented copy_from method in TensorImpl

implement properties and is_shape_aligned in TensorImpl

implement move constructor and move assignment operator for TensorImpl

remove unimplemented method error throw in TensorImpl constructor

fix type inconsistency

Merge remote-tracking branch 'origin/add-opencl-kernel-manager' into add-opencl-kernel-manager

ignore non-GPU devices

made compile kernel return the kernel

kernel compilation now throws on error

moved up catch block for not finding any opencl platforms

ignore non-GPU devices