Autofocus Camera Viewport

Many software packages have it, we need an autofocus camera in viewport, and maybe also the camera itself in render.

The viewport has priority, cause how many times while adjusting different angles, i always have to tediously go to the DOF distance, or move a dummy object aroud each time just to see how different angles are. Also to define which area is the focus area on the wievport would be great.

This also makes it possible to model with DOF enabled, letting you focus on the object.