Smart pointer for IDriverDependantBitmap

[ivan-mogilko]

1. Implement a custom smart pointer type for IDriverDependantBitmap pointer, which calls IGraphicsDriver::DestroyDDB in deleter. This may be just typedefs of std::unique_ptr and std::shared_ptr, with custom deleter.
2. IGraphicsDriver::CreateDDB* should return this smart pointer instead of a raw ptr.
3. Replace all instances of raw IDriverDependantBitmap* ptr around the engine code. Simplify DDB disposal to simply a call to smart pointer's "reset" method, or leave this for automatic destruction where possible to simplify the code.

NOTES.
It's possible, but not good to address a graphics driver through the global pointer which we unfortunately have now in the engine code. Instead the smart pointer could wrap this driver's pointer too (or DDB could).