Make DB class lockable with a read/write shared mutex from boost.
Make DB class lockable with a read/write shared mutex from boost.

thomaskrause/graphANNIS,thomaskrause/graphANNIS,thomaskrause/graphANNIS,thomaskrause/graphANNIS,thomaskrause/graphANNIS,thomaskrause/graphANNIS,thomaskrause/graphANNIS