[#32] Added sampler handle and sampler manager

config/Sources.cmake

include/vkcv/Core.hpp

include/vkcv/Handles.hpp

include/vkcv/Sampler.hpp

projects/first_triangle/src/main.cpp

src/vkcv/BufferManager.cpp

src/vkcv/Core.cpp

src/vkcv/SamplerManager.cpp

src/vkcv/SamplerManager.hpp