COB-99: Replace custom SmartPtr implementation (and boost::shared_ptr) with std::shared_ptr and std::unique_ptr

Use C++11 std::shared_ptr and std::unique_ptr instead of the custom SmartPtr (everywhere throughout RTCP) or boost::shared_ptr (gpu_wrapper.h).

In some instances, it was not completely obvious whether the pointer should be unique or shared, especially with Pool or Queue objects where strict ownership of the objects pointed to may be desirable. Furthermore, the custom Pool and Queue objects make it hard to properly use the unique_ptr in combination with std::move anyway. With the objective of removing SmartPtr in mind (rather than an even more extensive refactor operation), the following strategy was applied: use shared_ptr wherever unique_ptr causes problems but try use unique_ptr as much as possible.