Added multipage tiff reading to Dev 3.03

I checked out the 3.03 version to test out the pre-release version of Tesseract, and had the same question as the person in https://github.com/charlesw/tesseract/issues/50. I went ahead and exposed the method you mentioned in LeptonicaApi (as well as a couple of others that were required). 

I also updated the dll name since it seems to have been updated in the project, and fixed a null reference I was getting when the test project tried to initialize the engine, though that might not be as relevant. 

In any case, now the 3.03 version runs for me and it can handle multipage tiffs, so I thought I'd send it your way in case it saved you some time. If this isn't what you want, feel free to ignore.