Use shared libraries rather than static libraries

I've modified Tesseract-API to build a single shared library which is statically linked to tesseract and leptonica. This means that the only native file which has to be redistributed is `libtessbaseapi.dylib` (`.so` on Linux). Because it is statically linked, there is no need to redistribute any `.a` files. This reduces the .jar file on my Mac from 30.2MB to 14.5MB.

I've also removed the dependencies on zlib, libpng, libjpeg, giflib, libtiff, and libopenjpeg by building a minimal version with the appropriate ./configure flags for leptonica, as Tesseract-API doesn't need them.

I moved some of the C++ code around to simplify the native build, the JNI code now lives in `wrapper` and leptonica and tesseract are included as unmodified source trees, these `make install` to `build` using a custom PREFIX in ./configure. This should make it simpler to update tesseract and leptonica in the future.