Added InteropDotNet support

1. The [InteropDotNet](https://github.com/AndreyAkinshin/InteropDotNet) library was added (as source code) instead of obsolete `WindowsLibraryLoader`. Now the Tesseract is cross-platform AnyCPU library. Fixed https://github.com/charlesw/tesseract/issues/23 .
2. The binaries `liblept168.so` and `libtesseract302.so` were taken from Ubuntu 14.04 repo (original files `liblept.so.4.0.1` and `libtesseract.so.3.0.3`)
3. A bug with Leptonica signatures was fixed. Old signatures:

[DllImport(Constants.LeptonicaDllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "pixcmapSerializeToMemory")]
public static extern int pixcmapSerializeToMemory(HandleRef cmap, out int components, out int colorCount, out IntPtr colorData, out int colorDataLength);
[DllImport(Constants.LeptonicaDllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "**pixcmapSerializeToMemory**")]
public static extern IntPtr **pixcmapSerializeToMemory**(HandleRef colorData, int colorCount, int colorDataLength);

New signatures:

[DllImport(Constants.LeptonicaDllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "pixcmapSerializeToMemory")]
public static extern int pixcmapSerializeToMemory(HandleRef cmap, out int components, out int colorCount, out IntPtr colorData, out int colorDataLength);
[DllImport(Constants.LeptonicaDllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "**pixcmapDeserializeFromMemory**")]
public static extern IntPtr **pixcmapDeserializeFromMemory**(HandleRef colorData, int colorCount, int colorDataLength);